RU2556094C1 - Oil deposit development method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: according to the method geophysical survey of exploratory wells is performed by crossed dipole shear sonic imager. Oriented core is selected with further determination of directions of natural fracturing. Regional directions in maximum stress of oil-saturated rock are defined. According to findings injectors are placed along the regional directions in maximum stress. Producers are placed in between injectors thus forming developing method. Part of injectors occurred in fault zones and closer than 200m is introduced into operation as producers with their further transfer to injectors. When watering is higher than break even point and when it is required to maintain reservoir pressure at the deposit producers are transferred to injectors. Transfer of wells is made so that they form rows of injectors step by step along regional directions in maximum stress of oil-saturated rock and provide even oil displacement.

EFFECT: increased reservoir recovery due to more efficient and sound placement of well pattern within the area of oil deposit considering tectonic and geomechanic conditions of pay rocks occurring.

3 cl, 3 tbl, 8 dwg

Description

The invention relates to the development of oil fields using methods of displacing oil from the reservoir with water, in particular to the formation of a development system depending on the geomechanical conditions of occurrence of productive rocks. It represents the choice of the optimal location of wells in the hydrocarbon reservoir area, taking into account the azimuthal orientation of the maximum rock stresses. The method includes conducting geophysical surveys of wells, such as cross-dipole acoustic logs to determine the anisotropy of the azimuthal stress distribution in productive formations, microseismic monitoring during hydraulic fracturing to determine the direction of propagation of fractures, which coincides with the direction of the maximum stresses of the reservoir, studies of oriented core selected by definition directions of natural fracturing of rocks, if any, revealing disjunctive violations within the oil field.

The widely used method of the areal system for the development of oil deposits is known, the most common of which are five-, seven-, nine-point. Elements of the system with a five-point development scheme is a square, in the corners of which there are production wells, and in the center - injection wells. The ratio of injection wells to production wells is 1/1. In the seven-point development scheme, the system element is a hexagon with production wells at the top, injection in the center. The ratio of injection wells to production wells is 1/2. With a nine-point development scheme, the ratio of injection wells to production wells is 1/3 (Zheltov Yu.P. Oilfield Development: A Textbook for High Schools. - 2nd ed., Revised and supplemented. - M.: Nedra Publishing House, 1998 g.).

The disadvantage of this approach to the development system is the location of the wells without taking into account the geomechanical properties of the formation / layers, in particular the distribution of directions of maximum stresses, and the location of tectonic disturbances. The on-site development system is more “rigid” and does not allow the use of other injection wells from an element of the system without violating the geometric ordering of the wells. This leads to a more significant decrease in the oil recovery coefficient due to dagger and language breakthroughs of injected water to the bottom of production wells in almost all conditional series in the directions of maximum rock stresses and along tectonic disturbances, a decrease in the anhydrous period of operation, the appearance of a significant number of sites with high residual oil saturation not involved in the development.

There is a known method of developing an oil field (copyright certificate No. 1806262 dated March 30, 1993, ЕВВ 43/30, 43/20, bulletin No. 12 dated March 30, 1993), where, in order to eliminate the above-mentioned deficiencies, it is envisaged to: establish a deposit field on the area fracturing systems of the reservoir, drilling production and injection wells on the area of the reservoir, hydrocarbon production through production wells located within the fracturing systems at equal distance, and injection wells are located outside the fracturing eny. A method is also known (copyright certificate No. 1806261 dated 12/23/91, ЕВВ 43/30, 43/00, bulletin No. 12 dated 03/30/1993), in which at the exploration stage before drilling production wells based on space and aerial photographs of the territory, seismic studies for the reservoir, a map of the fracturing fault system is built, the results of which determine the locations for drilling wells within the fracture fault zones with subsequent drilling and oil and gas production.

There is a method of developing hydrocarbon deposits in fractured reservoirs (copyright certificate No. 2148166, ЕВВ 43/30 dated 10.27.2000), in which a complex of geophysical and borehole surveys is carried out, seismic sections and their paleoreconstructions are constructed on the basis of the obtained data, and geological ones are determined from them boundaries of reservoirs. Establish the location of zones of discontinuous disturbances, identify zones of neotectonic movements of the formation. Drilling productive wells near fracturing faults. A known method of developing an oil field (copyright certificate No. 2292453 of 01/27/2007, ЕВВ 43/30, 43/16), in which the location of the fracturing fault system is installed on the hydrocarbon reservoir area, production wells are located near them, and injection wells are located outside or within the zones limited by these discontinuous disruptions, determine the hydraulic connection of the discontinuous disruptions with the wells and / or other discontinuous disruptions and the composition of the hydrocarbon fluids and water extracted from them, resistance between wells and fractures and, with water inflow due to the oil circuit or from injection wells, increase the filtration resistances between wells and fractures by injecting waterproofing compounds through production or injection wells or through wells that are drilled for this purpose, on the circuit oil content near discontinuous faults on the water flow line, while transferring wells from one category to another; producing wells are placed parallel to fracturing faults at a given distance, taking into account the anisotropy of the permeability of the formation in different directions; place production wells near the intersection of several fracturing faults, in production wells not related to fracture system disturbances, reduce the filtration resistance between wells and fracture disturbances by directed perforation, hydraulic fracturing, drilling of horizontal trunks and sidetracks, and physicochemical effects; place injection wells in the inner part of the oil-saturated zone limited by discontinuous faults, the density of the mesh is selected inversely with the found permeability, taking into account its anisotropy in different directions, and these wells are transferred to production wells at the initial stage; place wells in a multilayer field with a choice of their profile as close as possible to the zones of discontinuous disturbances; producing wells are placed without intersection with discontinuous disturbances, the intersection is carried out in a hydrocarbon reservoir with a horizontal wellbore, sidetracking, hydraulic fracturing; place wells between adjacent hydrodynamically unrelated discontinuous faults, connecting the latter to the well by drilling additional wells in it, one or more of the wells being used for hydrocarbon production, and the other for pumping waterproofing compounds or as an injection pump; in the reservoirs, the hydraulic connection of the blasting faults with the wells and / or other blasting faults is determined by constant monitoring, taking into account the system of cracks and channels of low filtration resistance, the location of the producing and / or injection ones is changed; the location of discontinuous faults is established according to airborne geophysical studies, ground-based seismic surveys, spectral-seismic profiling, determination of tin (Sn), chromium (Cr), cobalt (Co) and their Sn / Cr, Sn / Co ratios during drilling according to cavernometry and the rate of change in drilling fluid absorption after drilling through vertical seismic profiling, hydraulic monitoring, tracer studies, temperature changes along the depth of the well, acoustic methods, adapt method ii geological simulation model, refine the position of faults geophysical methods; determine the source of oil in the reservoir of source rocks.

The disadvantage of these solutions is the lack of an idea of the adaptability of well placement on the oil field area, taking into account the anisotropy of the azimuthal distribution of horizontal stress values in productive formations, the irrational location of production and injection wells outside tectonic disturbances, implemented according to the "traditional" development system, hydrocarbon deposits without tectonic ones are not considered violations.

A known method of developing an oil field (copyright certificate No. 22911955 from 01.20.2007, ЕВВ 43/16), in which establish foci of seismic acoustic activity and fracture distribution for each reservoir, during the development process, record seismic acoustic emission over the area and in real time, by the combination of changes in seismic-acoustic emission and field development indicators, in particular isobar maps and water cut of wells, weakly drained, stagnant and washed zones are determined, phenomena of filtration flows initiate and intensify additional crack formation in weakly drained and stagnant zones to the level of recorded noise; to change the direction of the filtration flows, it is proposed to adjust the density of the grid of wells and the development system, organize new foci of waterflooding, drill additional wells and sidetracks, while establishing the relationship of production and injection wells with respect to the direction of fracture in the development elements, which ensures oil displacement, which is predominantly perpendicular to the propagation of cracks, in particular, in the in-line development element, injection wells, including horizontal and large cob trunks should be placed along the fracture direction line, and producing trunks, including horizontal wells and side trunks, should be parallel to this line; It is assumed that the radiation is constantly or periodically affected by physical radiation with the excitation and propagation of elastic waves, electromagnetic waves, and pulses in the geological environment for additional crack formation in weakly drained and stagnant zones.

The disadvantage of this method is that it considers deposits with fractured and fractured-pore reservoirs that are under development, identify weakly drained and stagnant zones, directions of fracture, optimize the existing system of development by mesh compaction, drilling additional wells and sidetracks in order to change the directions of the established filtration flows on development stage. The location of injection and production wells, including horizontal and sidetracks, parallel to the directions of fracturing is assumed only for additionally drilled wells in the developed deposits and in areas or individual elements where an in-line development system is formed due to these wells. The whole reservoir is not considered as a whole, hydrocarbon deposits with a pore reservoir with no fracture or insignificant amount are not taken into account, there is no idea of the adaptability of well placement in the oil field area taking into account the anisotropy of the azimuthal distribution of regional horizontal stresses in the reservoirs, which allows to increase the development efficiency, to reduce the proportion of weakly drained and stagnant zones from the beginning of the development, additional physical reservoir impact.

The objective of the proposed method is to increase the efficiency of hydrocarbon field development with comparable investments, as with "standard" development systems, to increase the oil recovery coefficient from the reservoir, which is achieved by more efficient placement of production and injection wells in the field, taking into account geomechanical and tectonic conditions productive breeds.

The problem is achieved by the fact that by the method of developing a hydrocarbon field, the location of discontinuous disturbances and the anisotropy of the propagation of stress of productive rocks, namely the azimuthal orientation of the maximum horizontal stresses, are established on the area of the hydrocarbon reservoir. Tectonic disturbances are determined: before drilling according to 3D / 2D seismic data; during drilling using cavernometry, as well as the rate of change in the absorption of the drilling fluid. The directions of maximum stresses are determined: prior to drilling, wells are accepted by analogy with neighboring oil fields under development with similar formations; when drilling exploratory wells and the first production wells, core-oriented core sampling is taken from the target interval of the formation with subsequent determination of the azimuthal direction of natural fracturing; after drilling exploratory wells, geophysical studies are carried out - cross-dipole acoustic logging (determines the geomechanical properties of the rocks, the directions of natural fracturing by measuring the velocities of longitudinal and transverse acoustic waves), while stimulating the flow using hydraulic fracturing, microseismic monitoring is also performed. Based on the data obtained, injection wells are placed azimuthally along the directions of maximum stresses of the productive formations. In the event that a zone of discontinuous violations is detected, an injection well located in the immediate vicinity of this violation, less than 200 m, is put into operation as an oil well with production to oil until the water cut of the produced product exceeds 95%, and / or above the profitability threshold under the existing at the time of the work, the cost of oil production, and / or, if necessary, maintain reservoir pressure during operation. Then the well is transferred under injection of the displacing agent, or into a piezometric fund to monitor the energy state of the development in the fault zone. In the process of field development, constant monitoring of the movement of filtration flows is carried out, the positions of discontinuous violations and local directions of maximum stresses are specified. Establish a hydrodynamic connection between injection and producing wells by the method of injection of tracer agents, hydraulic monitoring, geological field analysis, etc. Based on the obtained data on the zones of tectonic disturbances, local distribution features of the directions of maximum stresses, the development system is adjusted: some of the wells are transferred from one category to another - mining to injection, injection to mining. At the same time, injection wells try to move beyond the zones of tectonic disturbances and exclude cases where the production wells are located azimuthally on the same line with injection wells in the directions of maximum rock stresses.

The technical result consists in increasing the oil recovery coefficient, increasing the rate of oil production, achieved by placing production wells in the oil field, taking into account the directions of the maximum stresses of productive rocks, the presence of tectonic disturbances.

The essence of the method is as follows. Numerous studies, such as: cross-dipole acoustic logging, microseismic monitoring of hydraulic fracturing, tracer studies, hydraulic monitoring, geological and field analysis of the operation of injection and production wells in various fields of Western Siberia, show that the advancement of the main volumes of injected water and the manifestation of the most high speeds in the reservoir occurs along the directions of the maximum stress of the rocks. Fracturing hydraulic fractures also propagate along these directions and the natural fracture is oriented if present. Production wells located azimuthally in the same directions relative to injection wells are flooded first and often in an abnormally short time. The rate of water cut growth is sharper relative to neighboring wells located perpendicular to the line of maximum stresses. In zones of tectonic disturbances and areas adjacent to them, not more than 200 m, which is determined by geophysical studies and geological-field analysis, the direction of the regional maximum stresses changes its direction to completely coincide with the direction of development of these violations.

In FIG. 1, FIG. 2 shows variants of a three-row development system, respectively, with the traditional layout of wells and the proposed method. In FIG. 3, FIG. 4 depicts options for the areal seven-point development system, respectively, with the traditional layout of wells and the proposed method. In FIG. 5 shows a variant of the proposed method of a seven-point development scheme, which will be reduced to this form after the leading watering of production wells located azimuthally in line with the injection wells in the directions of the maximum stresses of the rocks and the subsequent transfer of the flooded production wells to injection wells. In all development schemes, injection wells are indicated by a four-pointed figure - pos. 1, mining circle - pos. 2, discontinuous violations by the dotted line - pos. 3, the azimuthal direction of the regional maximum stresses of productive rocks by the arrow - pos. 4, the lines of the rows of wells with a line - pos. 5, production wells converted to injection wells after reaching water cut thresholds, with a four-pointed figure, pos. 6.

Having arranged the rows of injection wells according to the proposed method along the regional directions of maximum stresses, a more uniform water flooding front is created. Initially, the injected agent moves along the line of injection wells along the channels of natural fracturing, creating cracks of “auto-hydraulic fracturing”, reaching the injection zones of neighboring wells in the shortest possible time. Then begins the intensification of movement in directions to production wells, in which the effect of piston displacement predominates. The number of dagger breakthroughs of the impact agent to the bottom of production wells decreases, their anhydrous period increases, and the oil recovery coefficient increases.

To determine the effectiveness of the claimed development method, calculations were carried out on a sectorial section of the geological and hydrodynamic model of the "Jurassic" deposit of one of the fields in Western Siberia, characterized by low reservoir properties, where an areal seven-point development system was implemented without taking into account the directions of maximum stresses. The model was built in the ROXAR software package, hydrodynamic modeling of the development process was carried out using the certified Tempest MORE v.6.7 software package that passed SPE testing in accordance with the requirements of the “Modeling Rules” and is widely used both in Russia and abroad. For numerical modeling of the development process, the model of "black" oil was used. The procedure of averaging the filtration-capacitive properties was carried out by weighing according to the corresponding volumetric characteristics in the IRAP RMS software package. The calculation of the indicators of reserves development was carried out on the basis of the actual technological operating modes of production and injection wells in the period from the beginning of development in 2006 to 01.01.2025 with a step of discretization of indicators for the 1st quarter.

29 wells were drilled and operated in this area. The proposed development method does not provide for a change in their number. According to 3D seismic data, no tectonic disturbances were found. The parameters of the filtration model of the site are presented in table 1, the geological and physical characteristics of the productive formation YUS-1 - in table 2, the relative phase permeability - in Fig. 4. The effectiveness of the proposed development method is determined by comparing the calculations of cumulative oil production shown in FIG. 5 and Table 3, which show that in the fifth year of development, the oil production rates under the new scheme begin to outstrip the base one and at the end of the billing period the excess is 107.7 thousand tons. An increase in oil recovery ratio occurred by 10%. In FIG. Figure 6 displays the residual oil saturation at the end of the calculation for the base and proposed development options, which indicates a more complete development of oil reserves over the area when implementing the proposed layout of wells, taking into account the distribution of the directions of the regional maximum reservoir stresses relative to the base.

Application of the proposed method in the oil industry will allow:

- increase the coverage of the developed formation by flooding by area;

- increase the anhydrous period of production wells;

- increase the rate of oil selection;

- increase oil recovery without additional capital investments.

Claims (3)

1. A method of developing an oil field, characterized by the fact that geophysical studies of exploratory wells are carried out using the cross-dipole acoustic logging method, an oriented core is selected with the subsequent determination of the directions of natural fracturing, regional directions of the maximum stresses of oil-saturated rocks are determined, and injection wells are located along regional directions according to the results obtained maximum stresses between the injection wells place production wells with the formation of a development system, part of the injection wells falling into the zones of tectonic disturbances and closer than 200 m are put into operation as production wells with subsequent conversion to injection wells, production wells, when they are flooded above the profitability threshold and, if necessary, maintaining reservoir pressure in the field , are transferred to injection wells and so that they gradually form continuous rows of injection wells along regional directions of maximum stresses second oil-saturated rocks and provides uniform oil displacement. 2. The method according to p. 1, characterized in that during the intensification of oil flows by hydraulic fracturing, microseismic monitoring is carried out. 3. The method according to p. 1, characterized in that when clarifying the distribution of regional directions of maximum stresses of oil-saturated rocks, the development system is adjusted, for which production wells are transferred to injection wells and injection wells to production wells, while injection wells must be outside the zones tectonic disturbances, and producing wells should not be in line with injection wells in the directions of maximum stresses of oil-saturated rocks.

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