Method for determining pore volume of dominant channel of well layer in low-permeability water-drive oil reservoir
By statistically analyzing dynamic and static data in low-permeability reservoirs, calculating the changes in water absorption and reservoir permeability before and after the development of dominant channels, and establishing a pore volume model, the problem of large discrepancies between calculated results and actual values in existing technologies has been solved, thereby improving the oilfield development effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DAQING OILFIELD CO LTD
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing methods are not applicable to low-permeability reservoirs and cannot accurately calculate the pore volume of dominant channels at the well group level, resulting in a large discrepancy between the calculated results and the actual situation in the field, which cannot effectively guide oilfield development adjustments.
By statistically analyzing dynamic and static data, the changes in water absorption, reservoir permeability, and pore volume before and after the development of dominant channels are calculated. Considering factors such as pressure sensitivity effect and variable start-up pressure gradient, a pore volume calculation model suitable for low-permeability reservoirs is established.
It improves the accuracy of calculating the pore volume of dominant channels in low-permeability reservoirs, provides a scientific basis for guiding the optimization of plugging agent parameters, and enhances the development effect and benefits of oilfields.
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Figure CN122148300A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of water-drive oilfield development and adjustment, specifically to a method for determining the pore volume of the dominant channel in a low-permeability water-drive reservoir well. Background Technology
[0002] The statements in this section provide only background information in connection with this disclosure and do not constitute prior art.
[0003] Water injection development adjustment is the main method for efficient oilfield development. With the deepening of development, major low-permeability oilfields both domestically and internationally are gradually entering the late-stage development phase with high water cut. Dominant channels are large-scale and complexly distributed, leading to severe inefficient and ineffective water circulation, reducing the effectiveness of water injection development and increasing development costs. Currently, conventional profile control and water shut-off methods are ineffective and have a short effective period, posing serious challenges to water cut control and decline rate control in oilfields. To improve the effectiveness of waterflooding development and increase water injection efficiency, it is necessary to determine the pore volume of dominant waterflooding channels to effectively guide the optimization design of plugging agent parameters, ensure plugging effects, achieve water cut control and decline rate control targets, and improve the effectiveness and efficiency of water injection development in oilfields. Therefore, accurately calculating the pore volume of dominant waterflooding channels is of significant practical importance for improving the effectiveness of waterflooding development in high-water-cut old oilfields.
[0004] Currently, there is limited research on methods for calculating the pore volume of dominant channels. Based on a survey and comparison with similar patented findings, existing methods exhibit the following problems.
[0005] (1) Existing methods are not suitable for low-permeability reservoirs. The specific reasons are: first, low-permeability reservoirs have a pressure-sensitive effect, which causes the permeability to decrease, and existing methods do not take into account the influence of the pressure-sensitive effect; second, low-permeability reservoirs are affected by the pressure-sensitive effect, resulting in permeability loss and dynamic changes in the starting pressure gradient. Similarly, existing methods do not take into account the fact of changing starting pressure gradient. Therefore, the existing methods are only suitable for medium-to-high permeability reservoirs and are not suitable for low-permeability reservoirs.
[0006] (2) Existing methods cannot calculate the pore volume of the dominant channel at the well group level because the current low-permeability reservoir well network is diverse and complex, with large differences in the physical properties between the target layers and strong vertical heterogeneity. Existing methods are only applicable to simple well groups with square or rectangular well networks and weak vertical heterogeneity reservoir conditions, and are not applicable to well groups with complex reservoir conditions.
[0007] For the reasons mentioned above, the current calculation results of the pore volume of the dominant channel differ significantly from the actual situation in the oilfield. This makes it impossible to fully describe the main characteristics of low-permeability reservoirs, thus failing to effectively guide oilfield development adjustments. Consequently, the applicability is poor, and the calculations cannot meet the needs of oilfields.
[0008] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art. Summary of the Invention
[0009] In view of this, this disclosure provides a method for determining the pore volume of the dominant channel in a well formation of a low-permeability water-drive reservoir. This solves the problem that existing methods are not applicable to low-permeability reservoirs and cannot calculate the pore volume of the dominant channel at the well group level. As a result, the calculated pore volume of the dominant channel currently differs significantly from the actual situation in the field and cannot fully describe the main characteristics of low-permeability reservoirs.
[0010] To achieve the above-mentioned objective, the method for determining the pore volume of the dominant channel in a low-permeability water-drive reservoir well includes:
[0011] The dynamic and static data of the target layer in the target well group are statistically analyzed, and the change in water absorption of the target layer before and after the development of the dominant channel is calculated using the dynamic and static data, the reservoir permeability k1 before the development of the dominant channel and the reservoir permeability k2 after the development of the dominant channel.
[0012] The dominant channel pore volume of the target layer is calculated using the dynamic and static data, the change in water absorption Δq, the reservoir permeability k1 before development, and the reservoir permeability k2 after development.
[0013] In this disclosure and possible embodiments, the formula for calculating the dominant channel pore volume of the target layer is:
[0014]
[0015] In the formula: V φ For the dominant channel pore volume, m 3 ;P Xwf The bottomhole flowing pressure of the oil well after the development of the dominant channel is measured in MPa; P iwf The bottom-hole flowing pressure of the injection well after the development of the dominant channel is measured in MPa; P i The original formation pressure is MPa; M o The stress sensitivity coefficient near the oil well is given in MPa. -1 M w The stress sensitivity coefficient near the injection well is given in MPa. -1 L is the distance between the injection well and the production well, in meters; μ is the water viscosity, in mPa·s; S w f represents water saturation. w ′(S w ) represents the water saturation level of S. wThe rate of increase in water production under the given conditions, %; φ is porosity; k1 is reservoir permeability before the formation of dominant channels, mD; k2 is reservoir permeability after the formation of dominant channels, mD; Δq is the change in water absorption of the target layer before and after the development of dominant channels, m. 3 ;r w Let be the radius of the wellbore, in meters (m).
[0016] In this disclosure and possible embodiments, the dynamic and static data includes:
[0017] After the development of the dominant channel, the bottom hole flowing pressure P of the oil well Xwf After the dominant channel develops, the bottom-hole flowing pressure P of the injection well iwf Original formation pressure P i Stress sensitivity coefficient M near oil wells o Stress sensitivity coefficient M near the injection well w Distance L between injection wells and production wells, water viscosity μ, and water saturation S w The rate of increase in water content f w ′(S w Porosity φ, wellbore radius r w Water absorption of the target layer before the development of the dominant channel q1, water absorption of the target layer after the development of the dominant channel q2, and bottomhole flowing pressure P of the oil well before the development of the dominant channel. XwfQ Before the development of the dominant channel, the bottom-hole flowing pressure P of the injection well iwfQ The effective thickness h of the target layer and the starting pressure gradient λ.
[0018] In this disclosure and possible embodiments, the formula for calculating the change in water absorption Δq of the target layer before and after the development of the dominant channel is:
[0019] Δq = q2 - q1;
[0020] In the formula: q1 is the water absorption of the target layer before the dominant channel develops, m 3 ;q2 represents the water uptake of the target layer after the dominant channel has developed, m 3 .
[0021] In this disclosure and possible embodiments, the formula for calculating the reservoir permeability k1 before the development of the dominant channel is:
[0022]
[0023] In the formula: P XwfQ Before the development of the dominant channel, the bottom hole flowing pressure of the oil well is measured in MPa; P iwfQ Before the development of the dominant channel, the bottom-hole flowing pressure of the injection well is MPa; h is the effective thickness of the target layer in m; λ is the starting pressure gradient in MPa / m.
[0024] In this disclosure and possible embodiments, the formula for calculating the reservoir permeability k2 after the development of dominant channels is:
[0025]
[0026] The beneficial effects of this invention are as follows:
[0027] The method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs of the present invention has the following innovative aspects compared with existing methods:
[0028] First, this method takes into account a wide range of factors, fully analyzes the reservoir development characteristics and fluid seepage characteristics of low-permeability oil reservoirs, and for the first time considers the influence of factors such as pressure sensitivity effect, variable start-up pressure gradient, and different well pattern.
[0029] Second, for the first time, a well-dominant channel pore volume calculation model (Formula 4) and a reservoir permeability calculation model (Formula 2 and Formula 3) applicable to low-permeability water-drive reservoirs were established.
[0030] The pore volume of the dominant channel in low-permeability water-driven oil reservoirs calculated by the method of this invention has a small difference from the actual situation in the field. The results can provide a scientific basis and guidance for the optimization design of profile control and water shut-off parameters in oilfields. Attached Figure Description
[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.
[0032] Figure 1 This is a flowchart of the method for determining the pore volume of the dominant channel in a low-permeability water-drive reservoir.
[0033] Figure 2 This is a schematic diagram of the PI3 layer in the Fang 6-Xie 19 well group according to an embodiment of this disclosure. Detailed Implementation
[0034] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.
[0035] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."
[0036] Figure 1The flowchart below illustrates the method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs disclosed in this paper. Figure 1 As shown, the specific steps of the method are as follows:
[0037] Step S10: Statistically analyze the dynamic and static data of the target layer in the target well group:
[0038] In this embodiment, by developing a data database and using indoor experimental data, the bottomhole flowing pressure P of the oil well after the development of the dominant channel is statistically analyzed. Xwf After the dominant channel develops, the bottom-hole flowing pressure P of the injection well iwf Original formation pressure P i Stress sensitivity coefficient M near oil wells o Stress sensitivity coefficient M near the injection well w Distance L between injection wells and production wells, water viscosity μ, and water saturation S w The rate of increase in water content f w ′(S w Porosity φ, wellbore radius r w Water absorption of the target layer before the development of the dominant channel q1, water absorption of the target layer after the development of the dominant channel q2, and bottomhole flowing pressure P of the oil well before the development of the dominant channel. XwfQ Before the development of the dominant channel, the bottom-hole flowing pressure P of the injection well iwfQ Dynamic and static parameters such as the effective thickness of the target layer h and the starting pressure gradient λ.
[0039] Step S20: Calculate the change in water absorption Δq of the target layer before and after the development of the dominant channel:
[0040] In this embodiment, the formula for calculating the change in water absorption Δq of the target layer before and after the development of the dominant channel is as follows:
[0041] Δq=q2-q1 (Formula 1)
[0042] In the formula: q1 is the water absorption of the target layer before the dominant channel develops, m 3 ;q2 represents the water uptake of the target layer after the dominant channel has developed, m 3 .
[0043] The parameters required for calculation in Formula 1 can be obtained through the development database. By substituting the statistically obtained data into Formula 1, the change in water absorption Δq of the target layer before and after the development of the dominant channel can be obtained.
[0044] Step S30: Calculate the reservoir permeability k1 before the development of the dominant channel:
[0045] In this embodiment of the disclosure, the formula for calculating the reservoir permeability k1 before the development of the dominant channel is as follows:
[0046]
[0047] In the formula: P XwfQ Before the development of the dominant channel, the bottom hole flowing pressure of the oil well is measured in MPa; P iwfQ Before the development of the dominant channel, the bottom-hole flowing pressure of the injection well is MPa; h is the effective thickness of the target layer in m; λ is the starting pressure gradient in MPa / m.
[0048] Substituting the statistical data obtained in step S10 into formula 2, the reservoir permeability k1 before the development of the dominant channel can be obtained.
[0049] Step S40: Calculate the reservoir permeability k2 after the development of dominant channels:
[0050] In this embodiment of the disclosure, the formula for calculating the reservoir permeability k2 after the development of dominant channels is as follows:
[0051]
[0052] Substituting the statistical data from step S10 into formula 3, we can obtain the reservoir permeability k2 after the development of the dominant channel.
[0053] Step S50: Calculate the pore volume of the dominant channel in the target low-permeability water-drive reservoir well:
[0054] In this embodiment of the disclosure, the formula for calculating the pore volume of the dominant channel in the target low-permeability water-drive reservoir well is as follows:
[0055]
[0056] In the formula: V φ For the dominant channel pore volume, m 3 ;P Xwf The bottomhole flowing pressure of the oil well after the development of the dominant channel is measured in MPa; P iwf The bottom-hole flowing pressure of the injection well after the development of the dominant channel is measured in MPa; P i The original formation pressure is MPa; M o The stress sensitivity coefficient near the oil well is given in MPa. -1 M w The stress sensitivity coefficient near the injection well is given in MPa. -1 L is the distance between the injection well and the production well, in meters; μ is the water viscosity, in mPa·s; S w f represents water saturation. w ′(S w ) represents the water saturation level of S. wThe rate of increase in water production under the given conditions, %; φ is porosity; k1 is reservoir permeability before the formation of dominant channels, mD; k2 is reservoir permeability after the formation of dominant channels, mD; Δq is the change in water absorption of the target layer before and after the development of dominant channels, m. 3 ;r w Let be the radius of the wellbore, in meters (m).
[0057] Substitute the statistical data from step S10 and the data calculated in the previous steps into formula 4 for calculation to obtain the pore volume of the dominant channel in the target layer.
[0058] Example
[0059] This embodiment of the invention takes the PI3 layer of the Fang 6-Xie 19 well group as the calculation object and calculates the pore volume of the dominant channel in the PI3 layer of the well group.
[0060] Figure 2 This is a well location map of the Fang 6-Xie 19 well group in the PI3 layer. The well group includes 5 wells, of which Fang 6-Xie 19 is a water injection well, and Fang 6-Xie 18, Fang 6-17, Fang 6-20 and Fang 6-Xie 21 are all oil production wells.
[0061] The following is the process for determining the dominant channel pore volume of the PI3 layer according to the method of the present invention. The specific steps are as follows:
[0062] Step S10: Statistical analysis of dynamic and static data of the PI3 layer in the Fang 6-Xie 19 well group:
[0063] By developing a data database and using indoor experimental data, the basic parameters of the PI3 layer in the Fang6-Xie19 well group were statistically analyzed, as detailed in Table 1.
[0064] Table 1. Dynamic and static data of the PI3 layer in the Fang6-Xie19 well group.
[0065]
[0066]
[0067] Step S20: Calculate the change in water injection volume Δq in the injection wells of the PI3 layer before and after the development of the dominant channel in the Fang 6-Xie 19 well group.
[0068] Substituting the data from Table 1 into Formula 1, the calculated change in water injection in the injection well before and after the development of the dominant channel is Δq = 5.3m. 3 .
[0069] Step S30: Calculate the reservoir permeability k1 of the PI3 layer before the development of the dominant channel in the Fang 6-Xie 19 well group:
[0070] Substituting the data from Table 1 into Formula 2, we obtain the reservoir permeability before the development of the dominant channel, k1 = 31mD.
[0071] Step S40: Calculate the reservoir permeability k2 after the development of the dominant channel in the PI3 layer of the Fang 6-Xie 19 well group.
[0072] Substituting the data from Table 1 into Formula 3, we obtain the reservoir permeability k2 = 114 mD after the development of the dominant channel.
[0073] Step S50: Calculate the dominant channel pore volume V of the PI3 layer in the Fang 6-Xie 19 well group. φ :
[0074] Substituting the data from Table 1 and the data calculated in the preceding steps into Formula 4, the dominant channel pore volume V of the PI3 layer in the Fang 6-Xie 19 well group is obtained. φ =303m 3 .
[0075] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for determining the pore volume of dominant channels in a low-permeability water-drive oil reservoir, characterized in that, include: The dynamic and static data of the target layer in the target well group are statistically analyzed, and the change in water absorption of the target layer before and after the development of the dominant channel is calculated using the dynamic and static data, the reservoir permeability k1 before the development of the dominant channel and the reservoir permeability k2 after the development of the dominant channel. The dominant channel pore volume of the target layer is calculated using the dynamic and static data, the change in water absorption Δq, the reservoir permeability k1 before development, and the reservoir permeability k2 after development.
2. The method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs according to claim 1, characterized in that, The formula for calculating the dominant channel pore volume of the target layer is: In the formula: V φ For the dominant channel pore volume, m 3 ;P Xwf The bottomhole flowing pressure of the oil well after the development of the dominant channel is measured in MPa; P iwf The bottom-hole flowing pressure of the injection well after the development of the dominant channel is measured in MPa; P i The original formation pressure is MPa; M o The stress sensitivity coefficient near the oil well is given in MPa. -1 ; M w The stress sensitivity coefficient near the injection well is given in MPa. -1 L is the distance between the injection well and the production well, in meters; μ is the water viscosity, in mPa·s; S w f represents water saturation. w ′(S w (S) represents the water saturation level. w The rate of increase in water production under the given conditions, %; φ is porosity; k1 is reservoir permeability before the formation of dominant channels, mD; k2 is reservoir permeability after the formation of dominant channels, mD; Δq is the change in water absorption of the target layer before and after the development of dominant channels, m. 3 ;r w Let be the radius of the wellbore, in meters (m).
3. The method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs according to claim 1, characterized in that, The dynamic and static data include: After the development of the dominant channel, the bottom hole flowing pressure P of the oil well Xwf After the dominant channel develops, the bottom-hole flowing pressure P of the injection well iwf Original formation pressure P i Stress sensitivity coefficient M near oil wells o Stress sensitivity coefficient M near the injection well w Distance L between injection wells and production wells, water viscosity μ, and water saturation S w The rate of increase in water content f w ′(S w ), porosity φ, wellbore radius r w Water absorption of the target layer before the development of the dominant channel q1, water absorption of the target layer after the development of the dominant channel q2, and bottomhole flowing pressure P of the oil well before the development of the dominant channel. XwfQ Before the development of the dominant channel, the bottom-hole flowing pressure P of the injection well iwfQ The effective thickness h of the target layer and the starting pressure gradient λ.
4. The method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs according to any one of claims 1-3, characterized in that, The formula for calculating the change in water absorption Δq of the target layer before and after the development of the dominant channel is: Δq = q2 - q1; In the formula: q1 is the water absorption of the target layer before the dominant channel develops, m 3 ;q2 represents the water uptake of the target layer after the dominant channel has developed, m 3 .
5. The method for determining the pore volume of dominant channels in low-permeability water-drive oil reservoirs according to claim 4, characterized in that, The formula for calculating the reservoir permeability k1 before the development of the dominant channel is: In the formula: P XwfQ Before the development of the dominant channel, the bottom hole flowing pressure of the oil well is measured in MPa; P iwfQ Before the development of the dominant channel, the bottom-hole flowing pressure of the injection well is MPa; h is the effective thickness of the target layer in m; λ is the starting pressure gradient in MPa / m.
6. The method for determining the pore volume of dominant channels in low-permeability water-drive reservoirs according to claim 5, characterized in that, The formula for calculating the reservoir permeability k2 after the development of the dominant channel is: