A gravity energy evaluation method for water-flooded oil reservoirs

Abstract

The present application discloses a gravity energy evaluation method for a water-driven oil reservoir, comprising: establishing a gravity energy evaluation chart for the oil reservoir based on an injection water driving strength equation; calculating the injection water gravity driving strength of the developed units using data of developed units in the oil reservoir and the injection water driving strength equation, and performing gravity energy classification on the gravity energy evaluation chart in combination with the injection water gravity driving strength of the developed units; plotting data of units to be evaluated in the oil reservoir on the gravity energy evaluation chart, and identifying the gravity energy category of the units to be evaluated based on the gravity energy classification; and solving the problem that there is no gravity energy evaluation method for water-driven oil reservoirs with large formation dips.

Description

Technical Field

[0001] The present disclosure relates to the technical field of oil and gas field development, and in particular to a study on the influence of gravity on water injection development in oil reservoirs with large formation dip angles. By utilizing this study, the strength of the gravity energy of the oil reservoir can be determined, and development units can be divided according to the strength of the gravity energy, and policies can be implemented in a classified manner, so that gravity energy can play a positive role in oil field development. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] For reservoirs with steep formation dips, gravity differentiation influences waterflooding, a fact that has been proven in both theory and practice. However, research conducted domestically and internationally has yielded no guiding findings on the relationship between gravity energy and waterflooding. Currently, the only relevant standard is the "Method for Evaluating Natural Energy of Reservoirs (SYT 6167-1995)," which defines effective gravity drive as "generally, formation dips greater than 15° and gravity factors greater than 10." Consequently, there is no method for evaluating gravity energy in waterflooding reservoirs.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the Invention

[0005] In view of at least one of the above technical problems, the present disclosure provides a gravity energy evaluation method for water-flooding oil reservoirs to solve the problem that there is no gravity energy evaluation method for water-flooding oil reservoirs with large formation dip angles.

[0006] To achieve the above-mentioned object of the invention, the water-flooding reservoir gravity energy evaluation method comprises:

[0007] Establish a gravity energy evaluation chart for the reservoir based on the injection water driving strength equation;

[0008] Calculating the gravity driving intensity of the injected water in the developed unit using the developed unit data of the reservoir and the injected water driving intensity equation, and performing gravity energy classification on the gravity energy evaluation chart in combination with the gravity driving intensity of the injected water in the developed unit;

[0009] The data of the unit to be evaluated in the oil reservoir are plotted on the gravity energy evaluation plate, and the gravity energy category of the unit to be evaluated is identified according to the gravity energy classification.

[0010] In an embodiment of the present disclosure, the method for establishing the gravity energy evaluation chart includes:

[0011] Given different values ​​of injection water gravity driving intensity, the air permeability corresponding to different formation dips under the given injection water gravity driving intensity is calculated according to the injection water driving intensity equation;

[0012] The relationship curves under different gravity driving intensities of injected water are drawn with the air permeability as the abscissa and the formation dip as the ordinate, and the logarithm of the ordinate is taken to obtain the gravity energy evaluation chart.

[0013] In an embodiment of the present disclosure, the injection water driving strength equation is:

[0014] Q wh =cK sin 2 a;

[0015]

[0016]

[0017] Where:

[0018] Q wh ——Injection water gravity driving intensity, in cubic meters per day per meter m 3 / (d·m);

[0019] K - formation air permeability, in millidarcy (mD);

[0020] α——stratum dip angle, in degrees (°);

[0021] ρ w - Density of injected water in grams per cubic centimeter (g / cm 3 );

[0022] μ w ——Injection water viscosity, in millipascals seconds (mPa·s);

[0023] g - acceleration due to gravity, in meters per second squared (m / s 2 );

[0024] b - parameters related to well spacing and well diameter;

[0025] c - parameter related to parameter b, injected water density, and injected water phase viscosity;

[0026] l——well spacing, in meters (m);

[0027] r w ——Well diameter, in meters (m).

[0028] In an embodiment of the present disclosure, a cumulative probability curve analysis method is used to classify the gravity energy.

[0029] The present disclosure has the following beneficial effects:

[0030] The water-driven reservoir gravity energy evaluation method provided by the present disclosure is difficult to apply uniformly because the viscosity of crude oil in different oil fields varies greatly and is difficult to apply uniformly, while the viscosity of water is not much different, and the vast majority of oil reservoirs at home and abroad are developed by water injection. Therefore, it is proposed to use water as a medium to evaluate the gravity energy of oil reservoirs. Therefore, the method disclosed in the present disclosure focuses more on the evaluation of the geological characteristics of the oil reservoir itself, avoiding the influence of many complex factors after development, and for the first time proposes the idea of ​​using water phase to evaluate gravity energy; secondly, under the guidance of the above ideas, the method disclosed in the present disclosure establishes a two-dimensional injection water gravity-driven intensity seepage model considering the well network factors, eliminates factors such as elastic energy, dissolved gas energy, and artificial water injection, and only considers the gravity-driven flow. , establish a calculation method for the injection driving intensity of water phase flowing into the production well; then, using the injection driving intensity calculation formula, with air permeability as the horizontal coordinate and formation dip as the vertical coordinate, according to the water injection driving intensity of each development unit of the oil reservoir, establish a corresponding curve family, and then establish a gravity energy evaluation plate for the specific oil reservoir; finally, according to the air permeability and formation dip data of each development unit of the specific oil reservoir, the gravity energy strength category corresponding to each development unit can be checked, and the specific oil reservoir can be guided to classify and implement policies for each development unit according to the gravity energy strength, so as to be used in the preparation of oilfield development plans and the formulation of water injection adjustment measures, to ensure that gravity energy plays a positive role in oilfield development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0032] Figure 1 is a flow chart of the water drive reservoir gravity energy evaluation method disclosed herein;

[0033] Figure 2 This is a gravity energy evaluation chart of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts not described in detail, those skilled in the art can also fully understand the present disclosure.

[0035] At the same time, unless the context clearly requires otherwise, words such as "include", "comprising" and the like throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, as "including but not limited to".

[0036] Figure 1 is a flow chart of the water drive reservoir gravity energy evaluation method disclosed in the present invention; Figure 1 As shown: The water-drive reservoir gravity energy evaluation method includes: step S10: establishing a gravity energy evaluation chart of the reservoir based on the injection water driving strength equation; step S20: using the data of the developed units of the reservoir and the injection water driving strength equation to calculate the injection water gravity driving strength of the developed units, and performing gravity energy classification on the gravity energy evaluation chart in combination with the injection water gravity driving strength of the developed units; step S30: obtaining data of the units to be evaluated in the reservoir, plotting them on the gravity energy evaluation chart, and identifying the gravity energy category of the units to be evaluated based on the gravity energy classification.

[0037] The embodiment of the present disclosure takes Haita Oilfield as an example to explain in detail the water drive reservoir gravity energy evaluation method of the present disclosure, and the specific steps are as follows.

[0038] Step S10: Establishing a gravity energy evaluation chart for the reservoir based on the injection water driving strength equation; the specific method used in the embodiment of the present disclosure is as follows:

[0039] 1. The injection water driving strength equation used in the embodiments of the present disclosure is:

[0040] Q wh =cK sin 2 a;

[0041]

[0042]

[0043] Where:

[0044] Q wh ——Injection water gravity driving intensity, in cubic meters per day per meter m 3 / (d·m);

[0045] K - formation air permeability, in millidarcy (mD);

[0046] α——stratum dip angle, in degrees (°);

[0047] ρ w - Density of injected water in grams per cubic centimeter (g / cm 3 );

[0048] μ w ——Injection water viscosity, in millipascals seconds (mPa·s);

[0049] g - acceleration due to gravity, in meters per second squared (m / s 2 );

[0050] b - parameters related to well spacing and well diameter;

[0051] c - parameter related to parameter b, injected water density, and injected water phase viscosity;

[0052] l——well spacing, in meters (m);

[0053] r w ——Well diameter, in meters (m).

[0054] 2. Establish a gravity energy evaluation chart for the Haita Oilfield, as follows:

[0055] Given different values ​​of injected water gravity driving intensity: 0.0005, 0.003, 0.01, 0.02, 0.06, 0.1, 0.2, 0.4, 0.6, 1.0m 3 / (d·m), and the air permeability corresponding to different formation dips under a given injection water gravity driving intensity is calculated based on the injection water driving intensity equation, as shown in Table 1:

[0056] Table 1 Value table of the horizontal axis (air permeability, unit mD) of the gravity driving intensity curve of different injected water (given formation dip angle)

[0057]

[0058] 3. According to the calculation results in Table 1, the relationship curves under different injection water gravity driving intensities are drawn with air permeability as the horizontal coordinate and formation dip as the vertical coordinate in the coordinate system, and the logarithm of the vertical coordinate is taken to obtain the following: Figure 2 Gravity energy evaluation plate shown.

[0059] Step S20: Calculate the gravity driving intensity of the injected water of the developed unit using the developed unit data of Haita Oilfield and the injection water driving intensity equation, as shown in Table 2. Figure 2 On the gravity energy evaluation chart shown, gravity energy is classified according to the gravity driving intensity of the injected water in the developed units. The specific method is:

[0060] The embodiment of the present disclosure adopts a cumulative probability curve analysis method to classify gravity energy according to the gravity driving intensity of water injected into the developed units, specifically into the three categories shown in Table 3.

[0061] Table 2 Calculation results of water injection driving strength of developed units

[0062]

[0063] Table 3 Gravity energy classification boundaries

[0064]

[0065] Step S30: Obtain the data of the unit to be evaluated in the oil reservoir, plot these data directly on the gravity energy evaluation plate, and identify the gravity energy category of the unit to be evaluated based on the gravity energy classification boundaries shown in Table 3. The specific method used in the embodiment of the present disclosure is as follows:

[0066] 1. Obtain the air permeability and formation dip data of each unit to be evaluated in Haita Oilfield;

[0067] 2. Draw the formation air permeability data and formation dip data of each unit to be evaluated Figure 2 On the gravity energy evaluation plate shown;

[0068] 3. According to Figure 2 The gravity energy evaluation chart shown in Table 3 and the gravity energy classification boundaries shown in Table 3 are used to determine the gravity energy category of each unit to be evaluated, and the gravity energy categories in Table 4 and Figure 2 The classification results are shown.

[0069] Table 4 Gravity energy classification results of the units to be evaluated

[0070]

[0071]

[0072] Based on the gravity energy classification results of the development units and the conventional technical means in this field, for Class I units with strong gravity energy, low-position simulated edge water drive is adopted to form a linear high-pressure propulsion front; for Class II units with medium gravity energy, the intensity of waist well injection is increased, mild water injection is adopted, the oil-water well ratio is reduced, and the effective injection direction is increased; Class III units have weak gravity energy, and its role does not need to be overly considered during the water injection process. A combination of skid-mounted booster water injection and measures modification is adopted to achieve area water injection.

[0073] In summary, the gravity energy evaluation method provided by the present disclosure and the gravity energy evaluation chart obtained by the method can be used for the preparation of oil field development plans and the formulation of water injection adjustment measures. For oil reservoirs with strong gravity energy, edge water gravity drive is adopted to make fuller use of gravity and overcome its adverse effects. For oil reservoirs with weak gravity energy, the mind can be liberated to implement internal area water injection, increase the displacement direction, and improve the development effect, so that gravity energy can play a positive role in oil field development and better guide the water injection development of specific oil fields. Because the disclosed method formulates adjustment countermeasures by distinguishing the energy strength of development units, it has the advantages of being simple, intuitive, and easy to operate, and can provide research ideas for improving oil field development effects.

[0074] The above-described embodiments are merely examples of implementation methods of the present disclosure, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications, equivalent substitutions, and improvements without departing from the scope of the present disclosure, and these modifications are all within the scope of protection of the present disclosure. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for evaluating gravity energy of a water-flooded oil reservoir, characterized in that: include: Establish a gravity energy evaluation chart for the reservoir based on the injection water driving strength equation; Calculating the gravity driving intensity of the injected water in the developed unit using the developed unit data of the reservoir and the injected water driving intensity equation, and performing gravity energy classification on the gravity energy evaluation chart in combination with the gravity driving intensity of the injected water in the developed unit; Plotting the data of the unit to be evaluated in the oil reservoir onto the gravity energy evaluation plate, and identifying the gravity energy category of the unit to be evaluated based on the gravity energy classification; The injection water driving strength equation is: Q wh =cK sin 2 a; Where: Q wh ——Injection water gravity driving intensity, in cubic meters per day per meter m 3 / (d·m); K - formation air permeability, in millidarcy (mD); α——stratum dip angle, in degrees (°); c - parameter related to parameter b, injected water density, and injected water phase viscosity; The calculation formula for parameter c is: Where: ρ w - Density of injected water in grams per cubic centimeter (g / cm 3 ); μ w ——Injection water viscosity, in millipascals seconds (mPa·s); g - acceleration due to gravity, in meters per second squared (m / s 2 ); b - parameters related to well spacing and well diameter; The calculation formula for parameter b is: Where: l——well spacing, in meters (m); r w ——Well diameter, in meters (m).

2. The water flooding reservoir gravity energy evaluation method according to claim 1, characterized in that: The method for establishing the gravity energy evaluation chart includes: Given different values ​​of injection water gravity driving intensity, the air permeability corresponding to different formation dips under the given injection water gravity driving intensity is calculated according to the injection water driving intensity equation; The relationship curves under different gravity driving intensities of injected water are drawn with the air permeability as the abscissa and the formation dip as the ordinate, and the logarithm of the ordinate is taken to obtain the gravity energy evaluation chart.

3. The water flooding reservoir gravity energy evaluation method according to any one of claims 1 to 2, characterized in that: The gravity energy is classified using a cumulative probability curve analysis method.

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