RU2601733C2 - Method of bazhenov formation deposits double medium geologic and hydrodynamic models constructing - Google Patents

Abstract

FIELD: geology; data processing.

SUBSTANCE: invention relates to geological and hydrodynamic simulation and can be used when solving tasks of searching, reconnaissance and design of oil deposits development under collectors complex structure. Summary: core material is studied with extraction of rocks lithological identification and determination of their main properties. Constructing detailed double medium three-dimensional geological model based on stochastic pixel parameters distribution method. Double medium hydrodynamic model is constructed (Kazemi model) with adaptation of formation parameters for deposit development history. Multivariate calculation of deposit development prognostic indices with selection of optimum variant and issue of recommendations for implementation of geotechnical measures are carried out. At that, for construction of geologic model cells types distribution statistical probability is determined, which are assigned with specific values of porosity, permeability, oil saturation, compressibility and connectivity between matrix and cracks by section of each deposit productivity zone. That is ensured by constructing local lithological cuts based on geophysical surveys materials interpretation with detection of law between geophysical parameters and lithologic composition of rocks. For separation of local productivity zones results of wells hydrodynamic research methods, seismic exploration complex data analysis are additionally used.

EFFECT: higher efficiency of searching, design and development of deposits under complex structure of reservoirs due to adequate geological hydrodynamic model.

1 cl, 5 tbl, 5 dwg

Description

The invention relates to the oil industry, in particular to methods of geological and hydrodynamic modeling of oil deposits and can find a place in solving the problems of search, exploration and designing of field development in conditions of complex reservoir structure.

Models of hydrocarbon deposits are widespread in the oil industry to determine various technical indicators of field development. In digital geological modeling, the formation is represented as a set of cells, each of which has a set of characteristic parameters (porosity, permeability, saturation, etc.). Thus, the model is a representation of the structure and properties of the reservoir and allows reproducing the filtration of multiphase liquid. Moreover, the reservoir model is representative if it is able to reproduce the historical performance of the wells (oil and water production, gas factor, etc.), as well as the energy state of the reservoir.

Building models of the Bazhenov formation, due to the peculiarities of the geological structure, cannot be carried out using traditional approaches of geological and hydrodynamic modeling. According drilling oil saturated formation thickness Yu ₀ bazhenovskoj suites varies in size from 10 to 40 m and an average of 26.5 m. The zones of high insulation layer U ₀ from other permeable complexes of more than 20 m thick clayey material fixed abnormally high formation pressure within 38 -55 MPa, due to the generation of hydrocarbons by kerogen, with an anomaly coefficient of 1.3-1.84 [1]. In addition, the productive formation has the following characteristic geological and physical features that cardinally distinguish it from other types of oil deposits [2]:

- sharp areal and layer-by-layer heterogeneity of FES of mosaic character;

- abnormally high oil saturation of rocks;

- in the productive zones, two types of collector are distinguished: cavernous-fractured and porous, differing in permeability by 1-10 thousand times;

- unusually high compressibility of oil-bearing rock in the field of plastic deformation during development at the depletion mode;

- extremely high brittleness of reservoir rock in the most productive intervals of the reservoir;

- ultra-low permeability (<10 ^-5 μm ² ) and the radius of the pore channels (r _cf = 50-100 ang.) of matrix rocks, high hydrophobicity of the pore collector, eliminating the entry of water into the pore space at any possible pressure of its injection into the reservoir;

- the suite over the entire area of its occurrence is a common fluid support for both water (hydrophobic state) and hydrocarbons (AVPD), dividing the Meso-Cenozoic deposits of the central part of Western Siberia into two hydrogeological complexes;

- The suite is a source of oil, developed over an area of about 1 million km ² .

A known method of constructing a geological and hydrodynamic model of a layered heterogeneous formation [RU 2135766, IPC E21B 49/00]. The method includes conducting geophysical studies of wells (GIS), geological and field studies of wells and laboratory studies of the properties of reservoir fluids and porous media, interpretation of GIS materials, building a detailed volumetric geological and hydrodynamic model of a layered heterogeneous formation by partitioning and correlation of sections according to GIS data, determining volumes cumulative oil production for producing wells and injection volumes for injection wells and issuing recommendations for geological and technical measures th. To divide and correlate sections, an adaptive approach is used, which consists in the accumulation of knowledge about the features of the geological structure of the formation by sequentially moving from identifying global patterns of change in geological and geophysical characteristics to identifying and taking into account local structural features. The disadvantage of this method in relation to the deposits of the Bazhenov formation is the impossibility of correlation of sections through the proposed interpretation of well logging data and the determination of high heterogeneity of the structure.

A known method of constructing geological and hydrodynamic models of oil and gas fields [RU 2475646, IPC E21B 49/00]. It includes determining the conditions of formation of rocks by material composition, as well as by texture and structural diagnostic features (lithological-facies analysis (LFA)), conducting mineralogical-petrographic analysis of sedimentary rocks of the studied object, interpretation of materials from geophysical research of wells (GIS), data processing by methods multidimensional mathematical statistics, characterized in that the facies are first established by a set of diagnostic features, after which verification is carried out using a set of mineral petrographic parameters, then using multivariate statistics methods, we analyze the relationships between quantitative (FES, GIS) and synthetic indicators, which are the qualitative characteristics of the extracted rocks obtained as a result of the LFA, such as texture and particle size distribution, encoded and representing a numerical form, based on which form a three-dimensional model of the field. In relation to the Bazhenov formation, this method does not allow for the sporadic distribution of various types of rocks to be taken into account both laterally and vertically. In addition, the method does not involve the construction of models that take into account the pore-crack type of the structure of the reservoir, in which there are significant differences in the nature of the movement of fluids in fractured and porous elements, which determines the features of fluid filtration in such media. Since it is the reflection of internal heterogeneity of properties that is the main task of geological modeling of deposits, traditional methods based on correlation of well sections and interpolation of reservoir characteristics, as applied to fractured reservoirs, are not effective enough [3].

Closer to the proposed invention is a method for modeling deposits of fractured carbonate reservoirs [US 20100138196 A1, IPC E21B 49/00]. The method includes characterizing a reservoir, generating a mesh, and sampling a geological model describing a fractured reservoir. Geological data may include information on deposits obtained from various sources: seismic surveys, core analysis, technological development indicators, well surveys, including during drilling and drilling. A general idea of the development of natural fractures is usually obtained from the analysis of individual fractures intersecting wellbores. Data describing the fracture network can be obtained from wellbore studies using a high-resolution electric imager, as well as core analysis. In addition, the data characterizing the fractures crossing a particular well can be obtained from observations during drilling, operational performance of the well, well logging results (for example, thermometry). The totality of the data obtained is used to describe the density of cracks. The propagation of cracks in the interwell space is carried out stachostically using the method of sequential Gaussian modeling. The resulting small-scale grid is a collection of many small cells and a network of cracks separating the cells. Each cell has a dataset: volume, permeability, porosity, interaction between cells, characterizing the relationship in crack-crack systems, matrix-cracks, matrix-matrix. Subsequently, the models are upscaled and calculated in a hydrodynamic simulator. The disadvantage of this method is the inability to take into account the significant lithological heterogeneity of the bedding of rocks, the individual characteristics of various differences of rocks (for example, the tendency to crack formation). In this regard, the model built by the known method does not give a qualitative characteristic of the Bazhenov Formation and the parameters of its occurrence.

Closest to the proposed invention by its technological essence is a method for modeling deposits of gas shales of the United States [US 20130346040 A1, IPC G06F 17/50]. It includes the construction of geological and hydrodynamic models (including a dual medium) by setting the reservoir properties of the reservoir based on a statistical analysis of the history of the development of the deposit, as well as transferring the obtained properties to the unexplored deposits - analogues for calculating the technological indicators of their development. The disadvantage of this technique is the construction of a detailed qualitative model only for well-studied objects with a fund of both exploration and production wells drilled. The selection of reservoir properties of poorly studied deposits is carried out by analogy with already known objects, which does not allow for a qualitative construction of the model due to the lack of comprehensive studies.

For the first time, a new approach to modeling is proposed, taking into account the peculiarities of the geological structure of the Bazhenov formation, which allows us to consider the proposed solution as meeting the criterion of "inventive step". The technical result of the invention is to increase the efficiency of prospecting, exploration, design and development of deposits in a complex structure of reservoirs by constructing an adequate geological and hydrodynamic model.

The essence of the proposed method

When constructing models of deposits of the Bazhenov formation, alternating lenses of various lithotypes both laterally and vertically determines the use of only stochastic geological models when constructing models and technological calculations, allowing for more detailed consideration of the peculiarities of an unusual reservoir type. The pore-fracture formation, as shown in the work of Warren-Ruth [4], reproduce the model with double porosity. In such models, a fractured formation is schematized by identical rectangular parallelepipeds separated by a rectangular network of cracks. For calculations, a mathematical model of Kazemi is used, in which a system of cracks and matrix blocks are considered as two continuous media embedded one into the other. A generalized scheme for constructing geological and hydrodynamic models of the Bazhenov formation deposits is shown in FIG. one.

In order to build a geological model of the Bazhenov Formation, at the initial stage, lithological classification of the rocks composing it is carried out. Based on the characteristics of the material composition, the predominance of one of the four main components distinguishes the following rocks: essentially clay, siliceous, carbonate and, finally, substantially kerogen. The remaining types of rocks can be obtained by combining the basic ones, and adding a texture-structural characteristic, to emphasize their ability in oil generation to transform into a fractured reservoir.

The physical basis for the diagnosis of distinguished lithotypes of rocks is the proven property of geophysical methods to reflect one or another feature of the material composition of the studied rocks. A lithophysical classification of rocks of the Bazhenov Formation has been developed, in which the main indicators of lithotypes of rocks are density, radioactivity and hydrogen content, i.e. their content of hydrogen-containing components and solid organic matter - kerogen. Eight main lithotypes of rocks are distinguished:

I - clayey rocks;

II - kerogen-siliceous-clay;

III - clay-kerogen-siliceous;

IV - clay-siliceous-kerogen rocks;

V - clay-kerogen-carbonate rocks (carbonates prevail over kerogen);

VI - kerogen-clay-carbonate rocks;

VII - carbonate rocks;

VIII - sand-siltstone rocks (only in the case of an anomalous section of the Bazhenov formation).

In FIG. Figure 2 gives the lithological section of the section of the Bazhenov deposits and rocks containing them in the coordinates "Qγ-W", their symbols are given. From this figure, a conclusion follows about a fairly clear differentiation of the identified lithotypes.

Table 1 shows the lithological and physical characteristics of the identified lithotypes. Further, the method involves the use of the first seven lithotypes for deposits of non-anomalous structure.

Based on all the accumulated experience of lithotype identification in the sections of sediments of the Bazhenov formation, the following algorithm was developed for automated breakdown of interpreted interlayers of the Bazhenov formation into lithotypes according to GIS data:

If J ^tubing > 0.85, then the interlayer refers to the 7th lithotype;

otherwise, if J ^tubing = (0.7-0.85), then the interlayer refers to the VI lithotype;

otherwise, if J ^tubing = (0.5-0.7), then the interlayer refers to the V lithotype;

otherwise, if K _Ker > 35%, then the interlayer refers to the IV lithotype;

otherwise, if K _Ker = (25-35%), then the interlayer refers to the III lithotype;

otherwise, if K _Ker = (10-25%), then the interlayer refers to the II lithotype;

otherwise, if K _Ker <10%), then the interlayer refers to the I lithotype,

where J ^tubing is a relative parameter of tubing, K _Ker is the volume fraction of kerogen.

As can be seen from the above decision-making sequence, when determining lithotypes of rocks of Bazhenov deposits, differences of rocks with a volume content of carbonates are primarily excluded. Then, depending on the volume content of kerogen, determined using radioactive logging, the remaining layers are assigned to a specific lithotype with the determination of the total voidness and oil saturation according to electric logging using the dependence of volumetric moisture on electrical resistivity. When analyzing the presented algorithm for the automated determination of lithotypes of rocks of the Bazhenov formation, it can be noted that the influence factor of volumetric clay content is not considered because it is impossible to accurately identify it in the deposits of the Bazhenov formation based on well logging data. An example of highlighting lithotypes of rocks of the Bazhenov formation based on the results of well logging is presented in FIG. 3.

Field geophysical studies can identify fractured working intervals of the reservoir, to establish the profiles of inflow and absorption. For these purposes, a whole range of studies is used: field-geophysical methods (flowmetry, thermometry, etc.), hydrodynamic studies (determination of permeability, piezoconductivity, hydraulic conductivity, productivity, fracture compressibility, initial and current reservoir pressures).

To determine the parameters characterizing the capacitive properties of rocks of the Bazhenov formation, a modified method for determining the total voidness is used, which provides for measuring the total volume and weight of the sample before its extraction and after complete extraction of hydrocarbons. In this case, the complete extraction of liquid hydrocarbons is achieved within 6-10 days of extraction.

Determining the values of total core voidness gives somewhat overestimated values of the useful voidness of the rocks of the Bazhenov formation. The overestimation is due to the dissolution in the extractant of a certain part of solid hydrocarbons and organics removed from the sample during the extraction process.

The capacitive properties of Bazhenov rocks in the context of wells are estimated by a set of radiometric methods with determination of the hydrogen content in the mineral skeleton, kerogen, and reservoir fluid. The average total hydrogen content of the rocks lies within 31%, of which 6-10% is accounted for by the pore-filling fluid. On average, 22% of all hydrogen is concentrated in mineral components: clay minerals and kerogen.

In order to evaluate oil productivity, select a development mode, oil recovery enhancement methods, substantiate calculation parameters, etc., the total voidness of the studied differences of the rocks of the Bazhenov formation is differentiated into pore and fracture.

Determination of the filtration properties of the rocks of the Bazhenov formation is carried out both according to the generally accepted methodology for gas under comprehensive compression of samples of 0.5-1.5 MPa, and for oil or its model under conditions simulating reservoir. Gas permeability determinations are carried out on standard cylindrical rock samples previously subjected to long-term extraction to free the pore space from hydrocarbons.

Due to the influence on the filtration properties of the rocks of the Bazhenov formation, prolonged extraction (formation of microcracks, the release of a highly viscous bitumen-like substance in a void space, etc.), the determination of gas permeability carries only a qualitative characteristic of the filtration properties of non-cracked or slightly cracked core samples. A more objective characteristic of this parameter is obtained by studying unextracted pre-preserved core under conditions simulating reservoir, where the filtrate is directly reservoir oil or its close model.

Experiments to determine the mechanical properties of rocks of the Bazhenov Formation are carried out on standard rock samples. To measure the compressibility of pores, samples are selected without visible cracks and with a crack void obtained from thin sections and not exceeding 0.1%.

In the installation chamber, the selected samples are preliminarily subjected to comprehensive compression (up to 20 MPa) in order to exclude possible plastic deformations. Then, the pressure is reduced to 0.3 MPa, after which the sample is stepwise loaded to 2, 3, 6, 12, 20, and 30 MPa. The exposure time of the sample at a certain pressure level was determined by the strain rate.

To determine the compressibility of cracks, samples with a fracture visible to the naked eye are selected. To determine the fracture voidness, the sample is saturated with water at a pressure of 1.5 MPa. Due to the hydrophobic state of the rocks of the Bazhenov Formation, water filled only cracks and caverns.

The mechanical properties of rocks of the Bazhenov formation in the context of wells are also evaluated according to the interpretation of acoustic logging materials.

The results of determining the averaged lithological and physical characteristics of the rocks of the Bazhenov formation are shown in table 2.

Due to the complexity of manufacturing thin sections of layered and fractured rock varieties of the Bazhenov Formation, as well as the impossibility of studying extended (larger than thin sections) cracks in them, studying the parameters of fracturing and cavernous rocks in ores and large grindings (> 5 cm) of core pieces (cutting samples core perpendicular to layering). At the same time, the surface of the ores and grindings is moistened with some kind of solvent (acetone was most often used) immediately after cutting them out. Due to the freer penetration of the solvent into the cracks, the oil in them interacts with the solvent, staining it in a dark color, which leads to the occurrence of existing natural cracks on the surface of the ore (Fig. 4). Artificial cracks formed during the selection, storage and preparation of the core for analysis, therefore, practically do not appear due to the absence or extremely small presence of light oil fractions.

Also, core samples after long-term storage are used to fix natural fracturing. Such ore is characterized by the release of heavy oil from cracks when heated to 200-340 ° C.

The density of the cracks is determined by crossing a line drawn on the surface of the ore in parallel or perpendicular to the layering. This value, as well as when calculating the thickness of the system of cracks in thin sections, is measured by the number of intersections per 1 m. An example of the distribution of microtrains over lithotypes of rocks is shown in the histogram of FIG. 5.

The general procedure for constructing a geological model is divided into three main stages:

1. the formation of a cube structural frame;

2. the formation of cubes FES for each set of distribution;

3. calculation of stocks and assessment of the reliability of options.

The geometrization of the simulated reservoir includes the task of a digitized roof and the formation of a package of parallel layers. The structural frame is automatically formed in the form of a uniform three-dimensional grid and is made taking into account the specified boundary values in the XY plane (the surface of the formation roof), as well as the number and dimension of cells for all vectors x, y, z. As a result of the construction, a “cube” of hypsometric marks is obtained that characterizes the spatial position of each calculation node in XYZ coordinates.

Based on lithotypes allocated in the Bazhenov formation, in order to build a geological model, cell types are determined that are assigned characteristic values of porosity, permeability, oil saturation, compressibility and connectivity between the matrix and cracks. Each environment has its own set of parameter values, an example of the selection of 27 cells characteristic of the Bazhenov formation is presented in Tables 3, 4. All types of cells are divided into massive (sigma is 0.001) and micro-layered (sigma is greater than 0.001).

The parametric filling of the model is carried out by setting the statistical distributions of rock types across all layers of the model. According to the core study, hydrodynamic studies, well log interpretation results and well tests, the most probable occurrence of the selected cell types in each interval (0.5 m) of the reservoir is determined. An example of the distribution of cells along the section of the Bazhenov formation is shown in table 5.

Due to the high lithological variability of the rocks of the Bazhenov formation according to the area of distribution, when designing the areas of deposits with a long extent, geological modeling is accompanied by local differentiation into productivity zones. To identify productivity zones, patterns of results of testing and development of wells with lithological composition of rocks, structural, tectonic, temperature and other factors are revealed. The most significant lithological factors are the content of kerogen rocks, which determine the oil and gas potential of the Bazhenov formation, dense carbonate rocks, the most competent for the formation of natural cracks and their conservation, essentially clay rocks with reduced oil saturation, incompetent for crack formation. At the same time, if zones are identified in close proximity to exploration and production wells according to the results of well logging and core studies, in the inter-well space (at a distance of 2-10 km from the wells) zoning of deposits is possible only on the basis of complex data from the results of seismic exploration. In this case, the volume fractions of cell types are determined for each of the productivity zones.

The lithology cube is formed in specialized software products that make it possible to create a cube of a three-dimensional discrete facies parameter based on the stochastic pixel method (for example, Roxar IRAP RMS Fades Indicators module or Schlumberger Petrel Facies Modeling module). Based on the distribution, the algorithm determines which of the facies (type of cells) to place in a particular cell. On this basis, each cell is assigned a code value of its type. Further, the cube of lithology (cell types) is supplemented by the corresponding parameters of porosity, permeability, oil saturation, compressibility, and matrix-fracture connectivity (σ).

Specialized software is used to describe the filtration processes, which allows calculating three-dimensional hydrodynamic models of oil, gas (dissolved) and dual medium water filtration (for example, Tempest-More by Roxar or Eclipse by Schlumberger).

The process of hydrodynamic modeling of oil fields consists of three stages [5], including: 1) data collection over a long development period and their subsequent transformation to a form convenient for use in modeling programs; 2) the process of reproducing the history of development and adaptation of reservoir parameters using software; 3) forecasting the production process, when a reservoir model adapted to the development history is used to calculate various options for field development in order to select the optimal one.

The process of constructing filtration models is reduced to a sequential quantitative description:

- geological parameters - the geometry of the filtration area and the FES of the modeled objects;

- physico-chemical properties of reservoir fluids and strength characteristics of reservoir rocks (for laboratory studies);

- relative phase permeability curves (according to laboratory research and field data);

- data on the location and condition of the wells, as well as the geological and technical measures performed on them.

When constructing filtration models of the Bazhenov formation, permeability is determined by the pressure functions that are characteristic of each distinguished lithotype of rocks. This is due to the ability of cracks to reduce their length and cross section (up to closure) when the reservoir pressure drops below a certain critical value.

The adapted constantly operating geological and technological model allows not only reproducing the current operational performance of the wells and the energy state of the development object, but also calculating the predicted values of development indicators, choosing directions for increasing the development efficiency, and also evaluating recoverable oil reserves of the Yu ₀ formation within the simulated areas .

The results of multivariate calculations of the development of deposits are used for further technical and economic analysis, with which they choose the optimal option for the exploitation of the field for a given period of time. The most optimal option is considered to provide the best ratio of the period of operation of the field and the total oil production, characterized by the shortest payback period of capital costs and allowing to achieve or exceed the approved oil recovery factor.

The list of graphic illustrations of the application of the proposed method

FIG. 1. A generalized scheme for constructing geological and hydrodynamic models of the double environment of the Bazhenov formation deposits.

FIG. 2. Lithological dismemberment of rocks of the Bazhenov Formation according to radiometry.

FIG. 3. An example of lithotype identification according to the geophysical characteristics of rocks of the Bazhenov formation along the Ai-Pimskoye field well.

FIG. 4. A system of intersecting fractures on a core sample of the Bazhenov formation, manifested by oil effusions.

FIG. 5. Histogram of the distribution of microcracks by ores in the rocks of the Bazhenov formation

Literature

1. Nesterov I.I., Petrosyan L.G., Sonic V.P., Khabarov V.V. Studies of oil and gas sections of the Bazhenov formation. - M., 1988 .-- 57 p.

2. Sonic V.P., Ilyin V.M. About the nature of AVPD in sediments of the Bazhenov formation of Western Siberia. On Sat "Oil and gas reservoirs at great depths." - M., MINHI GP, 1980.

3. Guidelines for the creation of permanent geological and technological models of oil and gas and oil fields (Part 2. Filtration models). - M.: VNIIOENG OJSC, 2003. - 228 p.

4. Barenblatt G.I., Zheltov Yu.P., Kochina I.N. On the basic concepts of the theory of filtration of homogeneous liquids in fractured rocks. - 1960. PMM. T. XXIV, no. 5.

5. RD 153-39.0-047-00. Regulation on the creation of PDGTM oil and gas and oil fields. - M .: VNIIOENG OJSC, 2000. - 100 p.

Claims (1)

A method for constructing geological and hydrodynamic models of a double medium of deposits of the Bazhenov formation and analog formations, including studying core material with lithotypes and determining their main properties, building a detailed volumetric geological model of a binary medium based on a stochastic pixel method of parameter distribution, building a hydrodynamic model of a double medium (Kazemi model) with adaptation of reservoir parameters to the history of reservoir development, multivariate calculations of predicted indicators of development deposit sides with the choice of the best option and the issuance of recommendations for geological and technical measures, characterized in that for constructing a geological model they determine the statistical probability of the distribution of cell types that are assigned characteristic values of porosity, permeability, oil saturation, compressibility and connectivity between the matrix and fractures along the section each zone of reservoir productivity, for which they build local lithological sections based on the interpretation of geophysical materials In order to identify areas of local productivity, the results of hydrodynamic methods of well research and analysis of complex data from seismic surveys are additionally used to identify the patterns between geophysical parameters and the lithological composition of rocks.

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