RU2087687C1 - Method for development of oil deposit - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: this relates to development of oil deposits with drilling new wells. According to method, increase of efficiency at later stage of development can be achieved by non-drilling of non-profitable wells and by involvement of resources which are undrained by existing net of wells. For this purpose, maps are drawn of initially extracted resources, actively extracted resources, undrained oil resources, and current oil saturated strata. Sections of locating active stock of wells are contoured on last map which are limited by value of current oil saturated stratum, and additional wells are drilled in points of contoured sections where value of undrained resources ensures profitable operation of well. EFFECT: high efficiency. 9 dwg

Description

 The invention relates to the oil industry, and in particular to methods for developing oil fields with drilling additional wells.

 A known method of developing oil fields, based on statistical processing of data on the state and operation of wells, using the analytical dependence of the optimal density of the grid of wells on a number of technological and economic factors [1] The disadvantage of this method is the lack of accounting for residual recoverable oil reserves (OIZN) for each well, as well as oil reserves not involved in development.

 There is a method of developing oil fields with an increase in the density of the grid of wells and a decrease in the ratio of the number of producing and injection wells [2] the disadvantage of which is the lack of consideration of undrained and weakly drained sections.

 Closest to the proposed method for the development of oil fields [3], including the construction of maps of the distribution of oil reserves and drilling of additional production wells in areas with maximum residual oil reserves or additional injection wells in areas poorly covered by oil-water displacement processes. The disadvantage of the prototype is the low efficiency due to the fact that essentially only active recoverable reserves are taken into account, because determination of hydrocarbon reserves is carried out using the displacement characteristics, which do not give an idea of the value of the residual balance of oil reserves in undrained and weakly drained zones.

 The problem and technical result solved by the invention are to increase the efficiency of oil field development and reduce costs at a late stage of development, by eliminating the drilling of unprofitable wells, as well as increasing oil recovery by involving reserves that are not drained by the existing network of wells.

 The problem is solved by sequentially building maps of initial recoverable reserves, active recoverable reserves, non-draining oil reserves and current oil-saturated thicknesses, outlines on the last map the location of the well stock, limited by the current oil-saturated thickness, not less than the maximum profitable drilling thickness, and additional wells are drilled at the points of the contoured sections, where the value of non-drained reserves ensures cost-effective operation with Vazhiny.

 A comparative analysis of the essential features of the invention and the prototype allows us to conclude that the proposed technical solution meets the criterion of "novelty."

 The inventive step of the claimed technical solution is confirmed by the novelty of its distinguishing features: for the first time, the authors proposed the construction of maps of non-drained oil reserves and their analysis together with maps of current oil-saturated thicknesses for selecting sections and drilling points for additional wells.

 The method is carried out by the following sequence of operations.

1. To build maps of initial recoverable reserves, the following maps are preliminarily built:
a triangulation network for the wells of the considered section of the reservoir;
areas of Voronoi;
specific drainage zones of producing wells;
initial balance oil reserves in drainage zones.

 Maps of initial recoverable reserves are constructed by drainage zones using the average projected oil recovery factor for a given area of the reservoir.

 2. Build maps of active (drained) oil reserves of producing wells using the displacement characteristics.

 3. Maps of non-drained oil reserves are built, and the values of non-drained reserves in each production well are determined as the difference between the initial recoverable reserves and the active (drained) reserves for this well.

 4. To build maps of the current oil-saturated thicknesses, a map of the current balance oil reserves for the wells drainage zones is preliminarily constructed, and the values of the current balance reserves for each well are determined as the difference between the initial balance reserves and the accumulated oil production for this well.

 Values of the current oil-saturated thicknesses for each well are determined by dividing the value of the current balance reserves by the area of the drainage zone of the well, the initial oil-saturated thickness, the average porosity in the drainage zone, and the average initial oil saturation.

 5. Determine the maximum cost-effective thickness for drilling a deposit using existing economic standards.

 6. On the maps of the current oil-saturated thicknesses outline the areas limited by the thickness not less than the maximum cost-effective drilling thickness. On the contoured sections, sealing wells are placed in zones with values of non-drained oil reserves, which ensure the profitability of the operation of these wells.

Example. The section of the oil reservoir of the BS ₆ formation of the Teplovsky oil field, developed by the areal 7-point inverted waterflooding system, is considered.

The following maps were sequentially constructed for the considered site:
a triangulation network (Fig. 1) obtained by splitting a grid of wells into triangles using the Delaunay triangulation method;
Voronoi regions (Fig. 2), i.e. areas whose points are closest to the given well;
areas (specific zones) of drainage of producing wells (Fig. 3) obtained by distributing Voronoi regions for injection wells in the closest producing wells;
the initial balance of oil reserves (thousand tons) for zones of drainage of producing wells (Fig. 4), calculated by the volumetric method according to the formula
Q _bal.nach = S • h _n • m • s _n • 10 ^-3 • ρ / b,
where S is the area of the drainage zone, m ² ,
h _n average drainage zone initial oil-saturated thickness, m,
m average porosity in the drainage zone, units

s _n average initial oil saturation of oil-saturated interlayers, units

ρ density of reservoir oil, t / m ³ ,
b volumetric coefficient of reservoir oil, units

initial recoverable oil reserves (thousand tons) (Fig. 5) calculated from the expression
Q _extracted Q _{ball start} • K _but ,
where K _{but the} average design oil recovery coefficient for the considered reservoir area, equal to 0.447;
active (drained) oil reserves Q _act (thousand tons) (Fig. 6), calculated for each of the producing wells according to the displacement characteristics;
non-drained oil reserves (thousand tons) (Fig. 7), determined from the expression
Q _subsoil Q _extracted Q _act ,
current balance oil reserves (thousand tons) by well drainage zones (Fig. 8), which are calculated by the formula
Q _bal.tec = Q _bal.nach -ΣQ _n ,
where ΣQ _n accumulated oil production for this well, thousand tons;
current oil-saturated thickness (m) (Fig. 9), determined from the expression
h _n.tek = Q _bal.tek • b / (S • m • s _n • ρ).
On these maps, well numbers and parameter values are indicated. On maps 4, 5, 6, and 8, an increase in the degree of shading corresponds to an increase in the indicated parameter. Existing wells are indicated by shaded circles (producing) and crosses (injection).

Based on the data of hydrodynamic calculations of the development indicators for a characteristic element of the BS ₆ formation development system at various limiting drilling thicknesses, using accepted economic standards, it was found that the minimum oil-saturated drilling thickness of this section of the reservoir is 3.1 m.

 Taking into account the obtained value on the map of current oil-saturated thicknesses (Fig. 9), the zones where the values of current oil-saturated thicknesses exceed 3.1 m are outlined (these zones on maps 7 and 9 are shown by hatching) (negative thickness values for some of the wells indicate that they drained the reserves of neighboring wells). However, an analysis of the maps of non-drained oil reserves (Fig. 7) showed that the main part of the residual oil reserves in these zones (with thicknesses greater than 3.1 m) is covered by active development of the existing well network (the central zone of the considered area is most actively developed) and drilling of additional wells in these areas it is not advisable (sections of wells 228, 240, 244b, 261, etc.). At the same time, within the zones with increased current oil-saturated thicknesses, undrained and weakly drained sections (Fig. 7) with high values of undeveloped reserves (wells 227, 229, 239, 257, etc.) that can be involved in active development by drilling additional wells.

 A joint analysis of maps of current oil-saturated thicknesses (Fig. 9) and maps of non-drained oil reserves (Fig. 7) allowed us to outline 6 additional wells for drilling, which are shown in Figs. 7 and 9 are shaded circles with numbers 1-6. Among them are two understudies (wells 1 and 6) of the abandoned wells 227 and 257, which did not take reserves from their drainage zones, and four wells located on the lines for tightening oil reserves. The values of recoverable oil reserves attributable to new wells are for wells 1-6 respectively 37.9; 34.5; 8.6; 13.7; 15.7; 29.4 thousand tons, and for understudy wells, the values of recoverable reserves were taken directly from the values of non-drained reserves of abandoned wells (Fig. 7), and for wells located on the production lines as the average value of non-drained reserves from two nearest producing wells, since the new a well will drain only part of the drainage area of nearby wells (on average half). For example, recoverable reserves for well 4 (13.7 thousand tons) are defined as the average between non-drained reserves for wells 246 (6.1 thousand tons) and 284 (21.3 thousand tons).

In order for the drilled well to be cost-effective, it is necessary that the recoverable reserves attributable to it exceed the minimum value sufficient to recoup the costs of its drilling and operation. For the conditions of the BS ₆ formation of the Teplovskoye field, the minimum cost-effective recoverable oil reserve per well is 25.6 thousand tons. Therefore, the drilling of wells 1, 2 and 6 will be economically feasible and they are recommended for drilling. Wells 3, 4 and 5 are impractical to drill.

 The method is industrially applicable and recommended for implementation by the development project of the Teplovskoye field.

Claims (1)

 A method of developing an oil field, including selecting sites for the location of the well stock on the basis of hydrocarbon reserves distribution maps, evaluating the profitability of drilling each well and drilling additional production and injection wells, characterized in that maps of initial recoverable reserves, active recoverable reserves, and non-drained oil reserves are sequentially constructed and current oil-saturated thicknesses, outline the areas of placement of the well stock on the last map, limiting emye current net pay thickness value of not less than the limiting value profitable thickness drilling and additional wells are drilled at points contoured portions, where the quantity of non-drainable stocks provides a cost-effective operation of the well.

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