RU2101475C1 - Method for development of nonuniform oil deposit - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: increase of oil recovery due to involvement in development of stagnant and blind zones with deteriorated collector properties can be achieved by method which implies drilling of designed number of injection and producing wells, watering and recovery of oil to surface with subsequent drilling of additional wells with view to volumetric nonuniformity of bed which is determined according to results of operating deposit, and by means of simulation procedure. Additional wells are drilled from horizontal wells or horizontal holes are drilled from old wells. Horizontal holes are drilled along line which connects stagnant areas of oil, and at presence of displacement zones, blind zones or zones with lower collector properties - along line connecting these zones. EFFECT: high efficiency. 2 dwg

Description

 The invention relates to the development of oil fields represented by heterogeneous reservoirs.

A known method of developing an oil field with heterogeneous formations by drilling the design number of injection and production wells, waterflooding and extracting oil to the surface, followed by drilling a small number of production wells, taking into account the heterogeneity of the formation [1]
The disadvantage of this method is the low oil recovery associated with incomplete coverage of the reservoirs due to lack of knowledge of heterogeneity of reservoirs and saturating fluids at the initial design stage.

The closest in technical essence to the proposed one is a method of developing a deposit, including drilling the design number of injection and producing wells, flooding the reservoir and extracting oil to the surface, followed by drilling additional wells that take into account volumetric heterogeneity of the reservoir. Volumetric heterogeneity is determined by the results of reservoir exploitation and modeling [2]
The disadvantage of this method is the low coverage of formations by water flooding due to the difficulty of detecting and involving stagnant zones of oil in vertical wells.

 The aim of the invention is to increase oil recovery by involving in the development of stagnant and deadlock zones and zones with impaired reservoir properties.

 This goal is achieved by a method including drilling the design number of injection and producing wells, waterflooding and extracting oil to the surface, followed by drilling additional wells that take into account volumetric heterogeneity of the formation.

 New is that additional wells are drilled with a horizontal wellbore or horizontal wells are drilled from old wells, and horizontal wells are drawn along a line connecting stagnant oil pillars, the location of which is determined by modeling, and in the presence of substitution zones, lenses, dead ends or zones with low reservoir properties along the line connecting these zones.

 In FIG. 1 shows the layout of design and additional horizontal wells with horizontal shafts that exposed residual oil pillars in a zone-uniform formation; in FIG. Figure 2 shows the layout of design and additional horizontal wells with horizontal shafts that exposed the residual oil pillars in pillars, in replacement zones and in dead ends.

 The proposed method is carried out in the following sequence.

 The field is drilled with a design grid of wells, its arrangement is carried out. Water is injected into injection wells and oil is extracted from production wells. During the operation of the field, oil, water and injection are measured. Refine oil reserves using reservoir parameters after wells obtained as a result of drilling a project fund. The geological structure is specified, the location of dead-end zones, lenses and zones with deteriorated reservoir properties is determined. After reaching the period of falling production, mobile reserves are determined using the displacement characteristics. Comparing the reserves calculated by the volumetric method and the displacement characteristics, the presence and amount of fixed oil concentrated in pillars, dead ends, lenses and near substitution zones are determined.

 Using two-dimensional or three-dimensional mathematical models of the reservoir, zones with minimal values of the pressure gradient are determined where the reserves of residual oil will be concentrated.

 Additional wells need to be drilled to engage in the development of reserves of residual oil concentrated in zones of minimal pressure gradient, dead ends, lenses and near replacement zones.

 Additional horizontal wells or horizontal wells from old wells are placed in such a way that the horizontal well intersects the residual oil zones. In the case when the distances between the stagnant zones are close enough for a horizontal well to pass through one well, they cover two or more zones, even if they are in different layers.

 Additional horizontal wells or horizontal shafts are drilled from old wells, mastered and put into production. Horizontal shafts drilled in productive formations in the area of oil stagnant zones create the connectivity of these zones with this production-taking well. Thus, previously fixed reserves, concentrated in pillars located in zones of the minimum pressure gradient, lenses, dead ends and in areas with poor collection properties, are involved in the development.

 During the operation of horizontal wells, due to the formation of an additional pressure gradient in the stagnant zones, the movement of previously fixed oil to these wells occurs. This leads to increased oil recovery.

 Example. The implementation of this method, consider the example of the development of two sections of the field (Fig. 1, 2). The sections were drilled with a design grid of wells, and their arrangement was completed. Water was pumped into injection wells and oil was extracted from production wells. Made measurements of oil, water and injection. We built lithological maps and calculated oil reserves, determined recoverable reserves from the displacement characteristics. In the first section (Fig. 1), 3064 thousand tons of geological and 1532 thousand tons of recoverable reserves, in the second section (Fig. 2), respectively 2145 and 1072 thousand tons. In the second section, significant zones (about 30) turned out to be a non-reservoir. Prior to the implementation of the proposed method, a total of 1,200 thousand tons of oil was extracted from two sites. The water content of the extracted products reached 50. We conducted modeling of plots using mathematical models of two-phase filtration in a two-dimensional region. The areas of least pressure gradients were determined. In the first section (Fig. 1), stagnant zones were formed on the tightening central rows between the producing wells. In the second section (figure 2) two lenses and three dead-end zones. The zones of residual oil were connected by lines and thus the trajectory of the horizontal trunk was outlined. In order to reduce the cost and simplify the technology of wiring a horizontal trunk, the trajectory was sought to be brought closer to a straight line shape, although in principle any configuration can be made.

 In the first section (Fig. 1) near stagnant zones, wells were selected for drilling horizontal lateral shafts. From each selected well, two horizontal shafts were projected in different directions in the direction of the pillars of oil. This option is most preferable from the point of view of saving material costs with maximum coverage of the pillars of oil. In the second section (Fig. 2), two new horizontal wells were projected to be drilled. One well will cover three stagnant zones (dead end zone and two lenses), the other well two stagnant zones (two dead end zones).

 Horizontal wells and lateral horizontal shafts were drilled. Let them go in prey. Recoverable reserves were determined using displacement characteristics. Recoverable reserves increased by 20 and amounted to 3125 thousand tons against 2604 thousand tons determined before drilling horizontal shafts and horizontal wells. Additional oil production for the entire period of exploitation of the sites will amount to 521 thousand tons.

Claims (1)

 A method for developing a heterogeneous oil field, including drilling a design number of injection and producing wells, waterflooding and extracting oil to the surface, followed by drilling additional wells that take into account volumetric heterogeneity of the formation, characterized in that additional wells are drilled with a horizontal wellbore or horizontal wells are drilled from old wells moreover, horizontal trunks are carried out along the line connecting the stagnant oil pillars, the location of which is determined by modeling , and in the presence of lenses, dead ends or zones with low reservoir properties along the line connecting these zones.

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