Collectors oil and Gaza are such rocks that are able to hold oil and gas and give them to pressure drop .

Any breed that contains pores, emptiness, cracks, can become a collector.

All oil and gas collectors are accepted to separate the terrigenous and carbonate.

Territory collectors. Breed - terrigenic type collectors consist of seeds of minerals and fragments of rocks of different sizes, sacred by cement of various types. Typically, these breeds are represented in different extent expired sandstones, aleurolites, as well as in the form of a mixture of them with clays and argillites. To characterize terrigenous collectors, their mineralogical and particle size distribution compositions are of great importance.

By mineralogical composition, terrigenous collectors are divided for quartz and polyminthic.

Quartz collector It is formed in nature under conditions when the grain of quartz has a quartz grain in the process of sedimentation. In this case, the formed breed has a sandy basis (up to 95-98%).

Polyminter collector It is formed if, in case of sedimentation, in addition to the quartz grains, a large percentage of grains is represented by field swaps and products of their chemical transformations. The formed breed has a significant impurity of clay differences (up to 25-50%), worsening its collector properties.

Carbonate collectors Mainly limestone and dolomites are composed. Among carbonate collectors is a special place biogenic or organogenic toles formed by the vital activity of organisms: corals, msnok, mollusks, diatoms of algae.

The largest fragments distinguish rocks:

The properties of the rock fit (capacity) and skip (permeability) through itself liquids and gases are called filtration and capacitive properties (FES).

The wetting space of rocks is represented by pores, caverns, cracks, biopusters.

Piathers Usually referred to empties between mineral grains and fragments of less than 1 mm. They are enclosed in the hard frame of the breed, called the matrix.

Kaverns - these are a variety of voids of more than 1 mm in size, formed mainly when leaching individual components or their recrystallization.

Cracks - A combination of gaps, disseminating the rock, in the bulk of the resulting in lithogenesis and associated with the formation of sedimentary rock.

Biopoustoty - These include internal voids in the sinks, inside coral skeletons, in limestone shells.

The capacity is determined by the porosity - the volume of emptiness in the breed. Porosity on genetic classification may be:

Primary -the voids are formed in the process of sedimentation and breeding (gaps between the grains - inter-rigid pores, between the layering planes, the cameras in the sinks, etc.).

AND secondary -pores are formed as a result of subsequent processes: the fracture and crushing of rock, dissolution, recrystallization, the occurrence of cracks due to the reduction of rock (for example, during dolomitization) and other processes. Porosity is measured as a percentage.

Introduction

carbonate collector Treshina

The problem of carbonate collectors of oil and gas in recent years has become extremely important both in our country and abroad. The number of deposits with carbonate collectors increases, oil and gas production from such deposits increases.

In our country, there are potential reserves of oil and gas deposits, dedicated to carbonate collectors, both in new areas and in older, where previously underestimated the prospects for the oil-bearing of carbonate rocks.

Carbonate fractured collector breeds in view of a sharp heterogeneity and complexity of the structure are a far from a grateful object for modeling. Over the past 20--25 years, many examples of miscalculations are known in determining their parameters to calculate oil reserves (gas). These examples indicate that we, in essence, are still on the way to solving this problem, although much in this direction has already been done.

Carbonate collectors

Carbonate rocks as oil and gas collectors are confidently competed with terrific formations. According to various sources, from 50 to 60% of the modern world stocks of HC is timed to carbonate formations. Among them are the best for quality collectors - carbonate rocks of reef structures. Oil and gas production, large in volume, is made from limestone and dolomites, including from Paleozoic and Precamibria; The largest deposits are open in Mesozoic and Paleozoic rocks, primarily in the countries of the Middle East. Large clusters in the reef structures of the Mesozoic age are open in the Gulf of Mexico Basin (Golden Belt, Campeche, etc.). Refortted flow rates (tens of thousands of tons per day) were obtained from the reef limestones). It is possible to note some link between the development of carbonate collectors and the amplification of carbonatonacopulation in geological history, which is associated with the total cyclicality of geotectonic development and the periodicity of sedimentation.

Carbonate collectors are characterized by specific features: extremely unbearable, significant variability of properties, which makes them comparison. They relatively easily occur a variety of diagenetic and catagenetic changes. The facial appearance of limestones is more than in chip rocks, affects the formation of collector properties. In mineral terms, carbonate rocks are less diverse than chip, but much more varieties have much more varieties. In the process of studying the collector properties of carbonate thickness, many authors have repeatedly emphasized the decisive role of the genesis of deposits, the hydrodynamics of the medium for the formation of the structure of the hollow space, which may be more or less favorable for the formation of collectors and determines the nature of subsequent transformations.

In general, carbonate rocks are easily subjected to secondary changes. "This is due to their increased solubility. The effect of secondary transformations in rocks with the primary inhomogeneous structure of the pore space (organo-deravenous differences) is especially large. By the nature of post-sedimentation transformations, carbonate rocks differ from the terrigenous, primarily it concerns the seal. Biogerm remains from the very beginning. Practically solid education, and then the seal is already slow. The carbonate Il can also quickly lithuage, while it has peculiar phenetry empties due to the release of gas bubbles. Small-grinding, lithuanian-algae carbonate precipitates are also quickly lithuaniable. The porosity is slightly reduced, but together with Thus, the significant volume of the pore space is "preserved".

In carbonate rocks, all types of voids are noted. Depending on the occurrence time, they can be primary (sedimentation and diagenetic) and secondary (post-diagenetic). In organogenic carbonate rocks, the primary supplements include intracrankinnye, including inside the reef buildings (in a broad sense - intraphorem), as well as interraultic. Some carbonate rocks may be chemogenic or biochemogenic origin, they form reservoirs of a reservoir type. These include primarily, as well as limestones with inter-or-violent voidness. Laminated or massive limestones are characterized by pellitormorphic or hikingrystalline, as well as crystalline structures. In crystalline, especially in dolomitized, breeds are developed intercrystalline (interzernaya) porosity.

Carbonate rocks to more than others are susceptible to secondary transformations (recrystallization, leaching, stylist formation, etc.), which completely change their physical properties, and sometimes the composition (dolomitization and smaller processes). This is the complexity of the allocation of natural tanks, since the same breed in some conditions can be considered as a collector with very high properties, and in others, if there is no rush, it can be a tire. The creation of secondary voids contribute to the dissolution processes (leaching), recrystallization, mainly dolomitization and smoldering or stylitization. Those or other processes affect differently depending on the gene type of rock.

Breaks in sedimentation, having regional importance, play a large role in the formation of high-intensive collector zones. Under the surface of the blurred and disagreement in the arrays of carbonate rocks, we can meet a closed zones associated with weathered and leaching. Within oil fields, highly productive horizons are confined to these zones. Along the fractured zones, dissolution takes up to large depths, in Kama Ural, it is noted at depths of up to 1 km.

The reefs are allocated "Sitty" usually leached limestone with porosity up to 60%, folded by corals, msanka, "spongy" large-engineer limestone (with porosity 40-45%), often cavernous and low-faceted limestones with individual pores and cavities, most often leaching. All varieties of limestone stand out inside the reef massif. The shiny and spongy differences are grouped into the zone of high porosity. Its formation in these zones is often associated with the removal of rocks on the surface and weathering. Debit of wells in different parts of reefs are sharply different.

Among the leaching phenomena, some special occasions having a local meaning should be noted, but sometimes manifested in a wide scale. Such an example can serve as chimobiogenic corrosion, manifested with the development of microflora on the BNK, which creates a sour medium, increases its aggressiveness and contributes to the dissolution of carbonates. Another example is the development of aster under the influence of carbon dioxide formed during the destruction of oil deposits. In both cases, the transition of the dissolved calcium carbonate below the sole deposits leads to the latter isolation from the rest of the reservoir. A special problem is the development of a deep carst (hypokartist) associated with various processes, in which in the deep zones of the sedimentary cover occurs at least short-term disclosure of cracks, as a result of which the admission of soda with depths increases, and, as a result, a depth card develops with the formation of collectors. The development of the hypocrist is obviously affected by the achievement of the state of the instability of calcite during immersion.

Within the basic groups of rocks, certain structural differences of rocks are distinguished. Organogenic limestone, as a rule, always sempulated and have smaller capacitive capabilities compared to biomorphic differences. The voids (pores) of organogenic and chip rocks are called the inner structure, since the internal structure of the components of these rocks is different.

In the chemogenic rocks of emptiness differ in the characteristics of the structure. In oolithic rocks, porous international space differs, the cutting cracks between and inside the concentrics of oolites and, finally, the negative-oolithic voids formed during the leaching of oolites (Fig. 1).

In crystalline (grain) limestones, the structure of the pore space (in case of dissolution) of the intercontrolle and cavernous. Pelitomorphic limestone usually have increased fracture compared to other types of carbonate rocks. In them, the most commonly developed steel stitches. It is usually visible to all transitions from the earliest stages - embryos and mute seams to typical stylolites. The formation of stylolites is associated with uneven dissolution under pressure. The clay crust on the surface of the stylicate seams is an insoluble residue of the breed. Often the horizons for the development of stylolites are the most productive in the context. They are permeable, due to the flushing of clay crusts

Cement carbonate rocks in structural terms differ from the listed groups. In principle, they are similar to conventional clastic rocks, but by the nature of the transformation, limestone

Fig. one Sulfatized dolomite with leaching oolithiums. Lower Cambrian Eastern Siberia, led. 60 (by ji.c. Chernova): A - the main mass, b - newly formed sulfate.

From the number of secondary processes in carbonate rocks, cementation, leaching, calcium and sulfatization are essential. Calcite cement is crystallized by evaporation of seawater flooding the beach, and partial dissolution of unstable minerals. Beach carbonate sand can harden in a few days. Similar almost instantaneous levities took place in past times. The further fate of the emptiness remaining in the framework may be different. When recrystallization, there is a significant change in the structure and texture of rocks. In general, this process is aimed at increasing the size of crystals. If during recrystallization part of the substance is taken out, porosity increases. The greatest secondary porosity possess unevenly recrystallized rocks. The growth of large crystals contributes to the formation of microcracks. The most effective effect on the formation of secondary emptiness has leaching and metasomatosis (mainly dolomitization).

Fig. 2.

Dissolution when leaching is manifested in different ways, depending on the greater or less dispersion of the particle breeding. Thin-dispersed components are stronger than this process. Solubility also depends on the composition of minerals and water: the aragonite dissolves better than calcite, sulfate water is more actively dissolved dolomite, etc. Analysis of changes in filter-capacitive parameters defined including leaching establishes them a very distinct link with structural-genetic types of rocks. An example of this is a major reef array of the Rannerperm and coal age of the Karachaganak field located in the northern side of the Caspian depression.

Another type of carbonate rocks and emptiness in them can be observed in ancient strata of Eastern Siberia in the Yubureno-Tomsk zone of oil and oil. Here, in the context of productive thickness, secondally modified recrystallized algae, stromatolyte dolomites prevail. Stalolite seams are widely developed in the rocks, often filled with clay-bituminous substance. The searches are widely developed. The arrays of carbonate rocky rocks when removing to the surface during the pre-investment break were weathered and counterting, which led to the development of cavernousness. Karst funnels and other niches were filled with delulvial-proluavial formations. Arrays are broken and fractured. Thus, collectors have a complex structure of the hollow space. From zones of high emptiness, high oil inflows were obtained.

Dolomitization is one of the leading factors in the formation of collectors. The formation of dolomite affects the ratio of magnesium and calcium water and the total value of salinity. With a higher concentration of salts, a larger amount of dissolved magnesium is required. In the process of diagenesis, dolomite occurs due to its predecessors - such as magnesian calcite. Primary diagenetic dolomitization does not matter to form collector properties. Metasomatic dolomitization in catagenesses is more important for converting collectors. For dolomit formation it is necessary to enter magnesium. Sources of it may be different. When catagenetic processes, in conditions of elevated temperatures, the solutions lose magnesium, exchanging it on calcium accommodating rocks. On the example of the Pripyatsky deflection, it can be seen that there is a clear dependence between the composition of brings and the intensity of secondary dolomitization. In those stratigraphic zones, where Devonian carbonate rocks are most strongly divided, the magnesium content in the brine falls sharply, it is used to form dolomite. When methagonetic dolomitization, the increase in porosity is especially noticeable, since the process goes into the rock with a rigid skeleton, which is difficult to compact. The total volume of the breed is preserved, void in it is increased by dolomitization. Following the consideration of carbonate collectors, it is necessary to once again emphasize that the structure of their pore space is extremely diverse, the undisturbed matrix has characteristics that are determined primarily by the primary structure, the cavernation strongly changes these characteristics, and trustedness creates as two superimposed friend On a friend of the emptiness system. All this determines the need for a special classification of collectors. Such an estimated genetic classification of collectors was proposed by K.I. Bagrintseva (Table 1).

The determining parameter of the proposed classification is the permeability, the limit values \u200b\u200bof which are taken from the analysis of the collector properties of rocks of various genesis and structural features. The minimum and maximum values \u200b\u200bof estimated indicators (porosity, gas-sustainability, etc.) are obtained from correlation dependences between permeability, porosity and residual water.

The most characteristic of the connection of residual water saturation with absolute permeability.

In the rocks as the filtration properties improve the amount of residual water decreases. The porosity may be different, while even high (more than 15%) the values \u200b\u200bof open porosity are in rocks with low filtration properties. Between the open porosity and residual water saturation, the connection is uncertain.

Table 1: Evaluation - Genetic classification of carbonate breeds - collectors containing gas and oil

Low porous rocks are always distinguished by a large water content, number dolomitization) permeable conclude a small amount of water, and poorly permeable - significant (more than 50%). In the classification scheme, all collectors are divided into three large groups A, B, B, inside which, in turn, highlights classes characterized by different estimated parameters, lithological and structural features. Groups A and B are presented in the main manifolds of pore and cavity-pore types, in - fractured and mixed types. In the rocks of the group A, primary emptiness predominate, the dimensions of which are increased in subsequent leaching processes.

In the breeds of group B developed sedimentation pore channels; Little role is played by emptiness leaching. The structure of the hollow space in the rocks of the group is significantly easier than in the group B, and the most difficult in group V. It is dominated by small winding, poorly communicating channels. Collectors I and II classes in a group A have mainly inherited high filtration and capacitive parameters. In III, IV and V classes, breeds are chosen-organogenic and biochemogenic with low primary collector properties. Secondary mineral formation, recrystallization, dolomitization, breaking, especially accompanied by leaching and removal of material, improve their properties. In VI and VII classes, breeds of such chemogenic and biohemogenic differences are isolated, the petrophysical characteristics of which will never reach high values. But here to a greater extent than in the high grades, another factor is shown - fracture. The type of void pore (for the matrix) and the fractured (as a whole for the collector). Therefore, the parameters of the matrix are separately given, which are mainly low, especially permeability, and separate crack parameters for which permeability is significantly higher.

Collectors of oil and gas It is called breeds, aligning natural tanks that can contain movable substances (water, oil, gas) and give them in a natural source or in rock during development in this thermobaric and geochemical settings. All known types of rocks can act as collectors (in one of the fields of Eastern Turkmenistan, even in the thickness of the salt contains a slight accumulation of gas).

Discern granular (interzernone), fractured, cavernous and biofuster collectors. There are often intermediate differences, especially fissure-cavernous and granular-cracks.

Granular are mainly sandy-aeuritic breeds and some differences in carbonate - olith, debris limestone, as well as residual rocks (seeling dressing). Empties of collectors are praises.

Cutting collectors can be sedimentary rocks, erupted and metamorphic. Cracks determine mainly the permeability of these formations.

In terms of sedimentary rocks, carbonate, but are also sandy-aeuritis and even clay, which were previously oil and gas producers. Cavernous collectors are most often associated with leaching zones with the formation of emptiness (cavern, caves) in carbonate and evaporite strata. As the main process, forming void, most often actuators.

Biofulatto collectors are associated with organogenic carbonate rocks, voids are intracelative and interstitial character. Describing the breed-collector, it is necessary, first of all, take into account its container, i.e. The ability to accommodate a certain amount of oil and gas, and the ability to give - to pass oil and gas through itself. The first property is controlled by the porosity of rocks, and the second is its permeability.

Porosity of rocks

The total volume of all emptiness in the breed, including pores, cavities, cracks, is called a general or absolute (theoretical) porosity. The total porosity is measured by the porosity coefficient, which is the ratio of the entire amount of the pore volume to the volume of the unit or percentage. Part of the pores in the breed is not interconnected. Such isolated pores are not covered by the flow of fluid when developing. In addition, isolated pores can be filled with water or gas. Therefore, the porosity is distinguished - the ratio of the volume of open pores to the volume of the breed.

Open porosity is always less theoretical. Some channels are excluded from the process of moving fluid and are ineffective due to their small diameter, the wettability of the walls of the channel, etc. The ratio of the amount of effective pores to the volume of the rock is called an effective porosity, which is expressed in the shares of a unit or percentage. Effective porosity should always be determined relative to the specific fluid and to the reservoir conditions. Its definition is possible by GIS methods or special fishing research. Sometimes the concept of the reduced porosity representing the ratio of the volume of the pore volume to the total volume of the breed matrix is \u200b\u200bused.

In natural conditions, the porosity of the sand-aleuritic collector depends primarily on the nature of the styling of grains, on the degree of their sorted, the escape, the presence, composition and quality of cement. In addition, the porosity depends on the manifestation and conservation of various sizes of the kavern and fracture due to secondary processes - leaching, recrystallization, dolomitization, etc. The structure and texture of breed-collectors have a large influence on the geometry of pore space. Under the structure of rocks means the external features of breed grains: their form, the nature of the grain surface, etc.; Under the texture - the nature of the mutual arrangement of grain grains and their orientation. In particular, the layered is one of the most important and widespread signs of the texture.

A significant effect on the interaction of breed collectors with fluid is the value of the pore surface. In the chip rocks, the total surface of the pores is in the inverse dependence on the size of the particles and is characterized by the value of the specific surface area:

where F is the coefficient of porosity; D - average grain diameter, see

The density of sedimentary rocks is determined in the range from 1.5 to 2.6 g / cm3 and for debris formations is in reverse dependence on porosity.

Carbonate rocks, as already noted, are often collectors. Primary porosity is characteristic of biogenic rocks, debris limestone, oncolite, spherolithic-clocks and olithic differences. It varies significantly in the diagenesis - when leaching, recrystallization and dolomitization occurs. Their first of these processes is determining the value for the counterting. Main formation can begin in the zones of increased fracture of rocks. Cavernous limestone are the most capacious manifiers. Unfortunately, the frequently formed cavities are filled with the calcite of later generation and other neoplasms. Dolomitization processes can increase the collector capacity up to 12%, and sulfatization and oxque processes significantly reduce it. In massive limestone and dolomites, the main capacity of the collector is formed, as a rule, due to fracture, reaching 2 - 3%.

The most common method of determining porosity is a volumetric method based on accurate fixation of the volume of filling fluid pore.

Permeability of rocks. Under permeability means the ability of rocks to pass through itself fluids. The experimental way was determined (Darcy), that the rate of steady filtration is proportional to the pressure difference:

where V is the filtering rate, m / s; m - dynamic viscosity, PA C; ΔР - Pressure drop on the segment A1, PA / M; KP - permeability coefficient, m2. The magnitude of permeability is expressed through the permeability coefficient of KP, M2. Determination of the permeability of rocks, along with the indicated characteristic of dimension (KP, M2), can also be carried out in d (Darcy) and MD; At the same time, the relation: 1D \u003d 10-15 m2 is used to transfer.

Permeability depends on the size of the pores, their interconnectivity and configuration, grains size, the density of their laying and the relative position, sorted, cementation and fracture. The magnitude of the permeability coefficient does not depend on the nature of the filtering fluid through the sample of the porous medium and on the filtration time. However, some deviations are observed in the experiment process. Thus, when filtering liquids in loose reservoirs and the presence of very small sand fractions is possible rearrangement of breed grains (suffusion) and clogging pore channels with small particles that change the permeability of the medium. Particles in oil suspended, in deposition, cause partial closure of pores, reducing permeability.

As a result of the isolation of resinous substances contained in crude oil, they are deposited on the surface of the grain grains of the collector, which leads to a decrease in the cross section of pore channels. When filtering water in collectors containing a small percentage of clay material in the composition of sandstone, clay boosts, which causes a decrease in the cross section of pore channels. When exposed to reservoir waters, especially aggressive, silica, the formation of colloidal silica in pore channels is possible - it also leads to their clogging. From clay minerals, according to data. Club (1984), maximally reduce the permeability of rocks of the Montmorillonite group minerals. A mix of 2% of montmorillonite to coarse quartz sandstone reduces its permeability of 10 times, and 5% of montmorillonite - 30 times. The same sandstone with an admixture of kaolinite up to 15% still retains good permeability (respectively 150 and 100-110 md).

The question of the connection between the two main parameters of collectors - porosity and permeability of the pores is quite complicated. The permeability is most closely associated with the sizes and their configuration, while the total porosity is essentially independent of the size of the pores. If in pore collectors permeability is proportional to the square of the pore diameter, then in the fractured collectors it is proportional to the cube of the splitness of cracks. The permeability and porosity in the zone of discontinuous dislocations depend on the conditions and the degree of filling them during recrystallization and the secondary cementation.

The overwhelming part of the collectors is represented by breeds of sedimentary origin, but other types are found among them. For example, in the Shaimskoye field in Western Siberia, oil occurs in the weathered granites of the Erezion protrusion of the foundation. In the Litton Springs deposit in Texas, oil occurs on the contact of the serpentinites and the accommodating limestones (Fig. 22).

In Cuba, oil is obtained from serpentines. In the Fibro field in Mexico, a part of the underground reservoir is formed by erupted rocks of the main composition. In Japan, some gas deposits are associated with tuffs and lavami. Slides oil and in the framework of the weathering of the foundation, folded by the erupted and metamorphic rocks.

According to the data obtained as a result of studying over 300 largest deposits in the world, oil reserves are distributed in collectors as follows: in the sands and sandstones - 57%; in limestones and dolomites - 42%; In fractured clay slates, weathered metamorphic and erupted rocks - 1%.

The largest number of deposits in the context of the sedimentary cover of the USSR is timed to the main productive layers of the terrigenous composition (the chalk sediments of Western Siberia, Carbon and Devon of the Russian Plate). From the lithologic-facial varieties among the terrigenous rocks, normal marine fine grained sandstones and aleurolites are most often found as oil and gas. Less frequently, oil and gas potential is associated with conglomerates and rocks of frequent fliesseviation.

With carbonate collectors currently linked less explored oil and gas reserves than terrified. In part, this can be explained by insufficient cultivation of carbonate rocks. The widespread development of carbonate collectors is assumed within the East Siberian Platform.

As follows from the above, clay stratas are very widespread. The clays perform the role of a fitting medium or local tires, the role of collectors - the conclusions of sands or lenses of sands, sandstones, carbonate rocks. However, at the beginning of the 20th century, oil and gas inflows were obtained and directly from clays in California (USA), then in other parts of the world and, finally, from the bituminous clays of the Bazhenov Sweet Western Siberia. As a rule, clay performing the role of the collector underwent significant changes in the process of lithogenesis (mainly different levels of epigenesis), which is identified by us with the process of catagenesis of the organic matter.

These clay rocks are essentially occupy an intermediate position between the clay and clay shale itself. According to T.T. Club (1984), they are predominantly hydrolyady, contain a significant amount of scattered OV, replete. The presence of a rigid frame of silicism and sorbed by clay minerals of OH, a hydrophobized surface of the montmorillonite from particles of clay minerals, which means the contact zones with each other and with other microcomponents of rocks, determine their industrial container. It was precisely the hydrophobization zones of contacts that predetermined them is quite easy separation, and later the return of that oil, which was concluded (T.T. Clubov, 1984). Tectonic activity also contributes to the formation of the capacitive space.

The porosity of collectors is due to the presence of pores of various sizes or cracks. Macropors (\u003e 1 mm) are highlighted. Among the latter there are superkapilly size from 1 to 0.5 mm, capillary - from 0.5 to 0.0002 mm and subcapillary pores<0,0002 мм. Породы, обладающие субкапиллярными порами, для нефти практически непроницаемы; к ним, в частности, относятся глины.

Studying terrigenous collectors performed by G.N. Parosio, B.K. Pasta, P.A. Karpov, E.E. Karnyushina, R.N. Petrov, I.M. Gorbanese, etc., showed a close correlation dependence between the type of collectors and the value of open porosity, on the one hand, and the level of catagenetic conversion to them with a depth, on the other. Determining are the processes of sealing breed-collectors and cracking. Data B.K. Pastovakov, in the Caspian depression, show that the corresponding seal and active cracking occurs at a depth of 3.5-4.0 km, and the resulting fracture porosity is about half of the total pore volume, and the crack permeability is measured by thousands of Money. A visual idea of \u200b\u200bthe types of collectors in the terrigenous rocks and the effects of catagenesis in the process of immersion gives them a summary table, composed of E.E. Carnish (Table 2).

For comparison, according to I.M. Gorbanese (1977), cracking in quartz and glauconito-quartz aleurolites of the Upper Eocene of the Western-Kuban deflection of the Scythian epigaigzinskaya slab begins with a depth of about 4.0 km. In the range interval from 0.6 to 5.0 km, the following distribution zones are allocated for various types of collectors: I type (up to 3.5 km) - pore; II (3.5-4.5 km) - the predominance of crack-pores in the presence of all other types; III (deeper 4.5 km) - fractured.

There is a basic classification of pores, channels and other voids based on the differences in the differences of the main forces causing the movement of fluids. MK Kalinko compiled a common classification table of all types of emptiness depending on their morphology and sizes (Table 3; dimensions limits are specified in each case).

A.A. Khanin applies more than MK Kalinko, gradation of pores in size, highlighting macropours is larger than 1 mm and micropores smaller than this value. The integrated use of the main scoreholders noted above has made it possible to propose on the basis of the recommendations of A.A. Khanina et al. As a practical (industrial), the following classification of collectors differing in the magnitude of porosity and permeability. First-class collectors include collectors with an effective porosity of over 26% and permeability - over 1000 MD; second class - collectors with effective porosity from 18 to 26% and permeability - from 500 to 1000 MD; the third - from 12 to 18% and permeability - from 500 to 100 MD; fourth - from 8 to 12% and from 100 to 10 md; Fifth grade - from 4.5 to 8% and from 10 to 1 md. Breed-collectors, having an effective porosity of less than 4.5% and permeability below 1 md, industrial significance does not have, forming sextal class collectors. The most complete classifications of carbonate collectors were developed by E.M. Lordov et al. (1962) and M.K. Kalinko (1957). Usually carbonate collectors are divided into three large groups: inter-rigorous, neglected and mixed. A group of inter-rigoric collectors includes several types, depending on the composition of the substance that fills the inter-rigorous spaces, and the degree of filling, and the necroupage - two subgroups: pore-cavern and fissure collectors; The recent porosity does not exceed 1.7-2%.

Carbonate rocks as oil and gas collectors are confidently competed with terrific formations. According to various data from 50 to 60% of modern world stocks, WC is timed to carbonate formations. Among them are allocated to the best collectors - reef structures with which almost 40% of WC reserves are associated in capitalist and developing countries1. Now oil mining from limestone and dolomites is about half of the world. Although the maximum number of similar deposits is associated with Paleozoic sediments, the largest deposits, including in reefs, are open in mesozoic rocks. This is primarily the Middle East with the world's largest oil field in Saudi Arabia. In the area, the largest amount of oil on the planet is concentrated mainly in carbohydrated rocks. The largest clusters in the reef structures of the Mesozoic age are open in the southern part of the Mexican Gulf basin, and record debates in tens of thousand tons per day are also obtained. It can be noted some link between the development of carbonate collectors and the amplification of carbonatonacpeting in geo logical history, which is associated with the total cyclicality of geotectonic development and periodicity of sedimentation.

Carbonate collectors are characterized by very specific features. They differ in extremely unbearable, knowledge of the variability of properties, which makes them comparison. They relatively easily occur a variety of diagenetic and catagenetic changes. The facial appearance of limestones is more than in chip rocks, affects the formation of collector properties. In mineral attitude, carbonate rocks are less diverse than chip, but the structural-tex tour characteristics have much more varieties. In the process of studying the collection properties of carbonate thickness, many authors have repeatedly emphasized the decisive role of the genesis of deposits, hydrodynamics of the carbonate formation environment in the embedding the structure of the hollow space, which may be more or less favorable for the formation of collectors and determines the nature of subsequent transformations.

In general, secondary changes (including tectonic order) are more affected by carbonate collectors than on terrigenous. This is due to the ease of their dissolution both at the depth and during intervals in sedimentation, metasomatase phenomena and greater efficiency of fracture development. Especially great

1 After strengthening the raeburization of the continental slopes, all these numbers can be changed significantly.

Table 15, emptiness in carbonate rocks

the effect of secondary transformations in rocks with a primary inhomogeneous structure of pore space (Detritogue differences like Vaxtown, Greynestene). As shown by K.I. Bagrintseva (1979), the most important for the formation of high containers and permeableness have genetic traits of carbonate rocks. On the basis of this provision, it has created a fundamental classification scheme of carbonate collectors, in which porosity, permeability and fluid saturation coefficients are tied to genetic Kim and textural-structural features of rocks. According to the character of post-semed transformations, carbonate rocks are different from the terrigenous, primarily this concerns the seal. The remains of bio-erms from the very beginning represent almost solid formation and are not further compacted. Clear sediments from uniform elements (sink wreckage) are lifted in the diagenesis very quickly. The porosity is slightly reduced, but at the same time the meaning of the pore space is "preserved".

In carbonate rocks, all types of voids are noted (Table 15). Depending on the occurrence, they can be primary (sedimentation and diagenetic) and secondary (post-imaging origin). In organogenic carbonate rocks, the vitreic vitreic materials are primary (in a broad sense of intraphorem), relict, as well as interrakovinic.

The creation of secondary voids contribute to the dissolution processes (leaching), recrystallization, metasomatase (mainly dolomitization and smoldering), stealitization, cracking of cracks. Those or other processes affect differently depending on the gene type of rock.

Breaks in sedimentation, which are of regional importance with the conclusion of deposits on the surface, play a large role in the formation of zones of high-intensive collectors.

Under the surface of erosions and disagreements in carbonate rock arrays, you can often find the requested zones associated with weathered and leaching. Within the oil fields, highly productive horizons are confined to these zones. Along the fractured zones, dissolution takes up to large depths, in Kama Ursal, it is noted at depths to 1.0 km.

Among the karst phenomena should be noted some special cases with local and regional meanings. One of the examples of such phenomena is chemobiogenic corrosion, manifested in the case of microflora development on BNK, which creates a sour medium, increases its aggressiveness and contributes to the dissolution of carbonates. Another example is the development of aster under the influence of carbon dioxide, which is generated in the destruction of oil deposits. In both cases, the transition of the dissolved calcium carbonate below the sole deposits leads to the latter isolation from the rest of the reservoir.

A special problem represents the development of a deep carst (hypokartist). This phenomenon is associated with various processes, in which in the deep zones of the sedimentary case, at least short-term disclosure of cracks occurs, as a result of which CO2 is increasing with depths and, as a result, a deep career is developing with the formation of collectors. Obviously, the development of the hypokartist is also affected by the achievement of the state of the instability of calcite at the pottery (as stated in the previous chapter).

IN the limits of the main genetic groups of carbonate rocks can be distinguished by certain structural differences of emptiness. Among the biomorphic differences between organogenic limestones, for example, in the reefs of the Nizhneperm in the pre-executive, intrafanochnoy and interdistrict emptiness are developed.

IN rifes highlighted "Sitty" limestones with porosity (hollowness) to 60%, isolated by corals, msnoks, brachiopods (see.

fig. 36), "Sponge" large-ferrous limestone (with porosity 4 0 - 45%), often cavernous and low-spirited limestone with individual pores and caverns, most often leaching. All varieties of limestone stand out inside the reef massif. Sitty and spongy are grouped into high porosity zones. Its formation in these zones is often associated with the removal of rocks on the surface and creature. Debit of wells in different parts of reefs are sharply different.

Among phytogenic limestones, stromatolys are allocated, having widespread development in the breeds of Cambrian, Vendian and Rhyphic age. Skeletal residues of these organisms have emptiness and can be collectors.

Organogenic limestone, as a rule, is always sizes and have less capacitive capabilities compared to biomorphic differences. Voids (pores) organogenic

Fig. 61. Empty and minor ka are true along the stylolite seam in limestone (led. 24, Nicoli +)

crowded rocks are called neglected, since the internal structure of the components of these rocks is different.

Chemogenic rocks according to the features of the structures of voids are on three groups.

1. In oolithic rocks, the porous space of interco-liter, cutting cracks between and inside the concentrations of oolites and, finally, Negatively oolithic emptiness, which are formed when siping ooliths.

2. In crystalline (grain) limestones, the structure of the pore space (in case of dissolution) of the intercontrolle and cavernous.

3. Pelitomorphic limestone usually have increased fracture compared to other types of carbonate rocks.

IN they are most often developed by stylistic seams. You can usually see all the transitions from the earliest stages of embryos and mighty seams to typical stylolites. The formation of stylolites is associated with uneven dissolution under pressure. The clay crust on the surface of the stylicate seams is an insoluble residue of the breed. Often the horizons for the development of stylolites are the most productive in the context. They permeable, due to the flushing of clay crusts, a gaping emptiness may form (Fig. 61).

Cement carbonate rocks in structural terms are different from the listed groups. In principle, they are similar to conventional clastic rocks, but by the nature of the transformation, limestone.

From the number of secondary processes, cement, recrystallization, dolomitization, leaching, calcium, sulfatization are essential important importance. Cement may begin very early and occur quickly, as it was clearly visible on the example of the Beach Rock of the Hawaiian Islands. Calcite cement is crystallized from sea water pouring the beach, and due to partial dissolution

unstable minerals. Beach carbonate sand can cure in a few days. Such almost instant lectification occurred in previous times. Further fate of the remaining in the frame of such "credit" voids can be different. When recrystallization, there is a significant change in the structure and texture of rocks. In general, this process is directed towards an increase in crystal sizes. If during recrystallization part of the substance is taken out, porosity increases. The greatest secondary porosity possess unevenly recrystallized rocks. The growth of large crystals contributes to the formation of microcracks.

The most effective impact on the formation of secondary voidness is leaching and metasomatosis (mainly dolo mitization). Dissolution when leaching is manifested in different ways, depending on the greater or less dispersion of the particle breeding. Thin-dispersed components are stronger than this process. Solubility also depends on the composition of minerals and water: the aragonite dissolves better than calcite, sulphate water is more actively dissolved by dolomite, etc. Analysis of changes in filtering and capacitive parameters defined including and addressed, establishes them a very distinct connection to structural agenetic types of breeds. A good example in this regard is a major reef array of Ranneperm and coastal age, located in the northern side of the Caspian Caspian.

The Karachaganak deposit is located under the solenous Kungur backyard at depths from 3750 to 5,400 m. In the productive thicker, bio -omermic and biomorphonetrite limestones are used in predominant development. Chemogenic and organo-degradious differences are lesser, dolomites, as limestone replacement products. According to the facies accessories, the breeds of the core of bio-manma, slope facies, intraforithus lagoons and loop deposits are distinguished. This is the usual scheme of the structure of all reef arrays. The best collector properties have the breeds of bio-maker nuclei, as well as the deposition of the inclinary phase of the early decoction age, which are already at a depth of about 4.8-4.9 km. They are characterized by porosity values \u200b\u200bfrom 10 to 23% and permeability (100-500) · 10-15 m2. Such high properties at high depths are determined by the fact that widely developed solution processes led to the formation of lenzide coarse areas with inherited cavernosis. Similar reef and pre-facies of chalk sediments in Mexico in the La reform area are the basis for the formation of good collectors with porosity from 14 to 26% and permeability in the tenth stakes of the square micrometer. Inherited leaching in rhygenic limestones K. I. Bag

Fig. 62. Distribution of collectors of various types in the reef massif of the Karachaganak field (according to K. I. Bagrintseva, etc.).

Types of collectors:

1 - caverno-pore, 2 - pore, 3 - complex (pore-fractured, crack-pore, fissure; facies zones: 4 - bioherm construction, 5 - internal lagoon; deposits: 6 - slope; 7 - plumes, 8 - Salt, 9 - Anhydrites, 10 - clay

rINTSEVA refers to the number of main factors for the formation of a collector of the special properties. The distribution of the facies zones and types of collectors of the Karachaganak field is illustrated in Fig. 62.

Dolomitization (and reverse breakdown process) is one of the leading factors in the formation of collectors. The formation of dolomite affects the ratio of magnesium and calcium water and the total value of salinity. With a higher concentration of salts, a larger amount of dissolved magnesium is required. In the process of diagenesis, dolomite arises at the expense of its predecessors, such as magnesian calcite. Primary diagenetic dolomiticization does not have a significant value for the formation of collector properties. Metasomatic dolomitization in catagenesses is more important for converting collectors. For dolomit formation it is necessary to enter magnesium. Sources of it may be different. One of the main brine associated with salty tiles. Indeed, on the example of the Prienysky deflection, it can be seen that there is a sufficiently distinct dependence between the composition of brings and the intensity of secondary dolomitization. In those housing areas where Devonian carbonate rocks are most strongly divided, the magnesium content in the brine falls sharply, it was used to form dolomite. With catagenetic processes in conditions of elevated temperatures, the solutions lose their magnesium, exchanging it to calcium accommodating rocks, as follows from the well-known Gaydinger and Marignac reactions. For example, by Marignac.

Classification of carbonate reservoirs

Carbonate rocks as oil and gas collectors are confidently competed with terrific formations. According to various data, from 50 to 60% of modern world hydrocarbon reserves are timed to carbonate formations. Among them are the best for quality collectors - carbonate rocks of reef structures. Oil and gas production, large in volume, is made from limestone and dolomites, incl. from Paleozoic and Precambria; The largest deposits are open in Mesozoic and Paleozoic rocks, before in the countries of the Middle East. Large clusters in the reef structures of the Mesozoic age are open in the Gulf of Mexico Basin (Golden Belt, Campeche, etc.). Refortted flow rates (tens of thousands of tons per day) were obtained from the reef limestones). It is possible to note some link between the development of carbonate collectors and the amplification of carbonatonacopulation in geological history, which is associated with the total cyclicality of geotectonic development and the periodicity of sedimentation.

Carbonate collectors are characterized by specific features:

1. Night suscomfortable, considerable variability of properties, which makes them comparison.

2. They relatively easily occur a variety of diagenetic and catagenetic changes.

3. The facial appearance of limestones is more than in chip rocks affects the formation of collector properties.

4. In the MIN-ORAL ratio, carbonate rocks are less diverse than chip, but by structural and textural characteristics have much more varieties.

5. In the process of studying the collector properties of carbonate thickness, the genesis of deposits and the hydrodynamics of the medium plays a decisive role to form the structure of the hollow space, which must be more or less favorable for the formation of collectors and determines the nature of subsequent transformations.

6. Carbonate rocks are easily subjected to secondary changes. This is due to their increased solubility. The influence of secondary transformations in rocks with the primary inhomogeneous structure of pore space is especially great.

7. According to the character of post-semed transformations, carbonate rocks differ from the terrigenous. Before all, it concerns the seal. The remains of biogerms from the very beginning represent almost hard education, and then the seal is already slow.

8. Carbonate Il can also be rapidly lithuage, while it has peculiar phenetry emptiness due to gas bubbles. Fine-cooled, self-cooled carbonate precipitates are also rapidly lifted. The porosity is slightly reduced, but at the same time significant volume of pore space'CONSERSVED''''''''''''''''l

In carbonate rocks, all types of voids are noted. Considering the dependence of the occurrence of appearance they are primary(sedimentation and diagenetic) and secondary(Postdiagenetic).

In organogenic carbonate rocks to primary Applicable voids, incl. Inside the reef buildings, as well as interraultic. Some carbonate breeds are chemogenic or biochemogenic origin, they form a reservoir type reservoirs. These include outerite, as well as limestone with inter- or intoleraiste voidness. Laminated or massive limestones are characterized by pellitormorphic or hikingrystalline, as well as crystalline structures. In crystalline, especially in dolomitized rocks, the intercrystalline (intergranular) porosity is developed.

Carbonate breeds more than others are subject to secondarytransformations (recrystallization, leaching, stylist formation, etc.), which completely change their physical properties, and sometimes the composition (the processes of dolomitization and smoldering). This is the complexity of the distinguishing of natural tanks, since the same breed in some conditions can be considered as a collector with very high properties, and in others, if there are no cracks, it can be a tire. The creation of secondary voids contribute to the dissolution processes (leaching), recrystallization, mainly dolomitization of smoldering or stylitization.

Those or other processes affect differently based on the genetic type of rock.

Cementation It can start very early and occur quickly, as it can be clearly seen on the example of the bichrocks. Calcite cement is crystallized due to the evaporation of sea water pouring the beach, and partial dissolution of unstable miners. Beach carbonate sand can harden in a few days. Such almost instant lectification occurred in previous times. Further fate of the remaining in the framework of such "emptiness should be different.

When recrystallization There is a significant change in the structure and texture of rocks. In general, this process is aimed at increasing the size of crystals. In case, during recrystallization, part of the substance is taken out, porosity increases. The greatest secondary porosity possess unevenly recrystallized rocks. The growth of large crystals contributes to the formation of microcracks.

The most effective impact on the formation of secondary volatility has leaching and metasomatosis (mostly dolomitization). Dissolution at leaching is manifested differently on the basis of a greater or less dispersion of the components of the particle breed. Thin-dispersed components are stronger than this process. Solubility is so depends on the composition of the miners and water: the aragonite dissolves better than calcite, sulphate water is more actively dissolved dolomite, etc. Analysis of changes in filter capacitive parameters defined, incl. Leaching, establishes them a very distinct link with structural-genetic types of rocks.

Dolomitizationit is one of the leading factors in the formation of collectors. The formation of dolomite affects the ratio of magnesium and calcium water and the total value of salinity. With a higher concentration of salts, a larger amount of dissolved magnesium is required. In the process of diagenesis, dolomite occurs due to its predecessors - such as magnesian calcite.

Primary diagenetic dolomitization does not matter to form collector properties. Metasomatic dolomitization in catagenesses is more important for converting collectors. For dolomit formation, magnesium intake is extremely important. Sources it is different. When catagenetic processes, in conditions of elevated temperatures, the solutions lose magnesium, exchanging it on calcium accommodating rocks. On the example of the Pripyatsky deflection, it can be seen that there is a clear dependence between the composition of brings and the intensity of secondary dolomitization. In those stratigraphic zones, where Devonian carbonate rocks are most strongly divided, the magnesium content in the brine falls sharply, it is used to form dolomite.

When methagenetic dolomitization, the increase in porosity is especially noticeable, since the process goes into the rock with a rigid skelter, which is difficult to seal. The total volume of rock is preserved, void in it due to dolomitization increases.

Reverse process rubberizing (Dedolomitization) is especially common in near-surface conditions. It is most actively underway in cuts where dolomites contain sulfates. When leakageing magnesiums of dolomites in solutions is connected to the radical SO 4 2- and is made in the form of an easily soluble MgSO 4. There is an increase in breed porosity.

But the transfer of sulfates by water often leads to opposite results from the point of view of the quality of collectors. Easily soluble Caso 4 is also easily precipitated and seals pores. Can also influence calcitizationwhich is often expressed in increasing the regeneration cuts and the narrowing of the pore space.

Finishing the consideration of carbonate collectors, it is necessary to once again emphasize that the structure of their pore space is extremely diverse. The undisturbed matrix has characteristics that are determined before the primary structure, the cavernosis strongly changes these characteristics, and the fracture creates as two emptiness superimposed on each other.

All this determines it is extremely important to draw a special classification of collectors. Such an estimated genetic classification of collectors was proposed by K.I. Bagrintseva (Table 2).

table 2

Evaluation genetic classification of carbonate collector breeds

The determining parameter of the proposed classification is the permeability, the limit values \u200b\u200bof which are taken from the analysis of the collector properties of rocks of various genesis and structural features. The minimum and maximum values \u200b\u200bof estimated indicators (porosity, gas-sustainability, etc.) were obtained from correlation dependences between permeability, porosity and residual water. The most characteristic of the connection of residual water saturation with absolute permeability.

In the rocks as the filtration properties improve the amount of residual water decreases. The porosity should be different, while even high (more than 15%) the values \u200b\u200bof open porosity are in rocks with low filtration properties. Between open porosity and residual water saturation Communication Neftee.

Low porcelain breeds of allocations are distinguished by a large content of water, and high-fuel have a dual characteristic: well-permeable concludes a small amount of water, and poorly permeable - significant (more than 50%). In the classification scheme, allone collectors are divided into three large groups A, B, B, inside which, in turn, highlights classes characterized by different estimated parameters, lithological and structural features. Groups A and B are presented in the main manifolds of pore and cavity-pore types, in - fractured and mixed types. In the rocks of the group A, primary emptiness predominate, the dimensions of which are increased in subsequent leaching processes.

In the breeds of group B developed sedimentation pore channels; Little role is played by emptiness leaching. The structure of the hollow space in the rocks of the group is significantly easier than in the group B, and the most difficult in group V. It is dominated by small winding, poorly communicating channels. Collectors I and II classes in a group A have mainly inherited high filtration and capacitive parameters. In III, IV and V classes, breeds are chosen and organogenic and biohemogenic with low primary collection properties. Secondary mino derivation, recrystallization, dolomitization, smoldering, especially accompanied by leaching and removal of material, improve their properties. In the VI and VII classes, the rocks of such chemogenic and biochemogenic differences are separated, the petrophysical characteristics of which will never reach high values. But here to a greater extent than in the high classes, another factor is manifested - fracture.

Classification of carbonate collectors - concept and types. Classification and features of the category "Classification of carbonate collectors" 2017, 2018.