CN106777628A - Consider the oil reservoir injectivity and productivity plate method for drafting of non-Darcy flow - Google Patents

Abstract

This application relates to a method for drawing reservoir injection-production capacity diagrams considering non-Darcy flow, the method comprising the following steps: (1) extracting the core of the target block, testing the threshold pressure gradient, and obtaining the characteristic expression of the threshold pressure gradient; 2) Collect basic reservoir data and calculate the start-up pressure gradient; (3) Correct the productivity calculation model of vertical well fracturing in low-permeability reservoirs, and obtain the correction factor of the productivity formula through regression training; (4) Set parameter change intervals and conduct sensitivity analysis, Complete the drawing of the production capacity calculation chart; (5) Calculate the equilibrium water absorption index of the water injection well, set different injection-production ratios, and complete the drawing of the water injection pressure chart. This application obtains the production capacity formula through the regression training of actual data, which overcomes the common problems of strong plane heterogeneity and large regional production-injection capacity differences in the development process of low-permeability oilfields, improves the accuracy of production capacity calculation, and forms a production-injection The integrated calculation chart is easy to guide the actual production of low-permeability oilfields.

Description

Drawing Method of Reservoir Injection-production Capability Chart Considering Non-Darcy Flow

technical field

The method belongs to the field of oil and gas field development, and in particular relates to a drawing method of a low-permeability oil reservoir injection-production capacity map.

Background technique

Among the proven reserves, low-permeability reservoirs account for a high proportion, accounting for more than 2/3 of the national reserves, and have great development potential. During the development of low-permeability reservoirs, there are typical characteristics of no injection and no production: water injection wells have high injection pressure, poor water absorption capacity, and even extreme situations such as pressure holding; most oil production wells can only be produced after fracturing. After water breakthrough, there is no liquid production index, so it is difficult to stabilize the reservoir production; therefore, it is of practical and important significance to accurately calculate the production and injection capacity of low permeability reservoirs.

At present, domestic and foreign vertical well fracturing productivity calculation models are mainly based on the start-up pressure gradient and stress sensitivity, but this is not universal for low-permeability oilfields with strong heterogeneity. The production capacity calculated directly by the production capacity calculation model has low accuracy and cannot guide actual production.

Contents of the invention

Aiming at the problems of low-permeability oilfields with strong plane heterogeneity and regional production-injection capacity differences, the present invention conducts related research on the productivity calculation method of low-permeability oilfields, and corrects the The steady-state productivity calculation model of vertical well fracturing in low-permeability reservoirs, through data regression training, obtains the productivity calculation formula matching the actual block, solves the problem of large differences in production and injection capabilities of low-permeability reservoirs, and applies it to reasonable productivity charts According to the balance of production and injection capacity and the characteristic pressure equation of water injection, the drawing of the water injection pressure chart is completed, and the two sets of charts are superimposed to form the application chart of the integration of production and injection to guide the actual production.

To achieve the above object, the present invention adopts the following technical solutions:

The drawing method of reservoir injection-production capacity chart considering non-Darcy flow includes the following steps:

Step 1: Extract the core of the target block, test the starting pressure gradient, and obtain the characteristic expression;

Step 2: Collect basic reservoir data and calculate threshold pressure gradient;

Step 3: Correct the productivity calculation model of vertical well fracturing in low-permeability reservoirs, and obtain the correction factor of the productivity formula through regression training;

Step 4: Set the parameter change range, conduct sensitivity analysis, and complete the drawing of the production capacity calculation chart;

Step 5: Calculate the equilibrium water absorption index of the water injection well, set different injection-production ratios, calculate the water injection volume of the water injection well, and complete the drawing of the water injection pressure chart.

Compared with the prior art, the present invention has the following beneficial effects:

1. Considering the characteristics of non-Darcy flow in low-permeability reservoirs, revise the calculation model of steady-state productivity of vertical well fracturing;

2. According to the characteristics of different injection-production units in different oil reservoirs, the production capacity calculation model matching the specific injection-production units is obtained by regression, which overcomes the problems of strong heterogeneity in low-permeability oilfields and large differences in regional production and injection capabilities;

3. According to the principle of production-injection balance, through the characteristic curve of water injection, the application chart of production-injection integration with guiding significance is obtained, which is convenient for practical application in production.

Description of drawings

Fig. 1 is a schematic flow chart of the drawing method of reservoir injection-production capacity chart considering non-Darcy flow;

Fig. 2 is the minimum starting pressure gradient measurement experimental device;

Figure 3 is the relationship curve between the start-up pressure gradient experiment and the permeability;

Figure 4 is the production capacity calculation chart;

Fig. 5 is a water injection indicating curve;

Figure 6 is the integrated drawing of injection and production.

detailed description

As shown in Fig. 1, the drawing method of reservoir injection-production capacity chart considering non-Darcy flow includes the following steps:

Step 1, extracting the core of the target block, testing the starting pressure gradient, and obtaining the characteristic expression; specifically, including the following steps:

(1), select the target block of the oil reservoir, extract the core of the target block, dry the core, measure the permeability by gas, and then soak the core in standard brine for more than 40h; the salinity of the standard brine is 10000mg/L , the viscosity is 0.9038mPa·s;

(2), assemble and install the starting pressure gradient test experimental device:

The experimental device for starting pressure gradient test includes three parts: high-pressure displacement pump, core holder, and capillary with scale, as shown in Fig. 2, which can quickly and accurately measure the minimum starting pressure gradient. The high-pressure metering pump mainly provides high-precision flow or high-precision constant high-pressure liquid or gas displacement, including a liquid displacement module and a gas displacement module, and is equipped with computer software to control injection pressure and injection volume, and can be designed in three phases ( Gas, oil, water) core analysis test system;

(3) Use a high-pressure displacement pump to slowly inject fluid into the saturated core. By observing the movement of the gas column in the capillary at the outlet end, when the gas column has a unit displacement of 1 mm, it is judged that the driving pressure has overcome the minimum starting pressure of the core, and the minimum starting pressure is determined. pressure range, stop the pump, and close the inlet valve;

The injection fluid is experimental kerosene with a viscosity of 1.6166mPa·s.

(4) When the gas column in the capillary no longer moves and the reading of the precision instrument remains unchanged, record the instrument pressure value P _g , and further obtain the minimum starting pressure gradient of the core as:

Among them, G is the minimum starting pressure gradient of the core; p _g is the recorded instrument pressure value; L is the length of the core.

(5), the computer makes a scatter diagram of the processed experimental data, and performs simple data fitting to obtain the characteristic expression of the starting pressure gradient;

Step 2, collecting basic reservoir data and calculating the threshold pressure gradient; specifically, the following steps are included:

(1) Collect basic data such as production data, reservoir physical properties, and fluid properties of the target block;

The production data refers to production pressure difference, liquid production volume, and fracture length; reservoir physical properties refer to effective thickness and stress sensitivity coefficient; fluid properties refer to permeability and viscosity.

(2), utilize the characteristic expression that the starting pressure gradient test experiment obtains, calculate starting pressure gradient;

Step 3: Correcting the productivity calculation model of vertical well fracturing in low-permeability reservoirs, and performing regression training to obtain the correction factor of the productivity formula; specifically, the following steps are included:

(1) The productivity formula of vertical well fracturing in low-permeability reservoirs considering non-Darcy flow is as follows:

Among them, q is liquid production rate, k is permeability, h is formation thickness, μ is viscosity, α is stress sensitivity coefficient, p _e is reservoir pressure, p _wf is bottomhole flowing pressure, ( _pe -p _wf ) is production pressure difference, x _f is the fracture length, G is the starting pressure gradient, u _e and u _w are intermediate variables (u _e ≈ ln(2R _e /x _f ), u _w ≈0).

The productivity formula of vertical well fracturing is simplified, and the influencing factors β1, β2, β3, β4, β5 are added to revise the productivity formula. The revised capacity formula is as follows:

(2) Substituting the basic data of the reservoir into the revised productivity formula, constructing the equation group of the objective function, and constructing the optimal objective function equation group as follows:

f(x)= _qqactual

Among them, q is the calculated liquid production rate; q is _actually the actual liquid production rate; f(x) is the objective function; x is the input parameter; n is the number of production wells in the target unit; z is the objective function equation group.

(3) Using the optimization iterative method to carry out regression training on the equation group, obtain the influencing factor coefficients β1, β2, β3, β4, β5, and substitute them into the revised production capacity calculation formula, so as to obtain the production capacity calculation formula matching the target block;

(4) Test the accuracy of the regression production capacity calculation formula. If the accuracy is less than 10%, output the capacity formula; if the accuracy is greater than 10%, continue the next regression training until the accuracy requirement is met;

Step 4. Set the parameter change range, conduct sensitivity analysis, and complete the drawing of the production capacity calculation chart; specifically, the following steps are included:

(1) Set the parameter change interval, conduct sensitivity analysis on the production capacity formula, compare the production capacity change range, and determine the main controlling factors affecting the block production capacity;

(2), count the average value of the non-main control factors, and set the change interval of the main control factors;

(3) Draw a production capacity calculation chart;

Step 5. Calculate the balanced water absorption index of the water injection well, set different injection-production ratios, and complete the drawing of the water injection pressure chart; specifically, the following steps are included:

(1) Statistical data of water injection pressure and water injection volume of injection-production units, and calculate equilibrium water absorption index and water injection starting pressure of water injection wells;

The water absorption index is the daily water injection volume of the water injection well under the unit water injection pressure difference, which reflects the water injection capacity of the water injection well and the water absorption capacity of the oil layer;

(2) Set different injection-production well ratios, and draw injection characteristic curves under different water injection methods. The formula for calculating the water injection volume is shown in the following formula:

J _w' = J _w ×C

q _inj ＝J _w' ×(p _f -p _c )

Among them, J _w is the equilibrium water absorption index; C is the injection-production ratio; J' _w is the water absorption index; p _f is the water injection pressure; p _c is the water injection starting pressure; q _inj is the water injection volume of the injection well;

(3) Superimpose the water injection indication curve with the production capacity calculation chart to form an integrated injection-production chart;

Example

Step 1. Extract the core of the target block, test the starting pressure gradient, and obtain the characteristic expression;

An injection-production block in reservoir A is selected, Table 1 shows the experimental data of threshold pressure gradient, and Fig. 3 shows the scatter diagram made by the data processed by the computer and the fitting curve of the relationship between threshold pressure gradient experiment and permeability

Table 1 Start pressure gradient experiment data

Permeability (md) 10.2 22.6 12.0 2.8 4.1 2.32 Starting pressure gradient (MPa/m) 0.105 0.604 0.082 0.406 0.328 0.528

The fitting relationship between the threshold pressure gradient and the permeability is as follows:

G＝ ^{1.1811k-0.995}

Step 2, collecting the basic data of the reservoir, and calculating the threshold pressure gradient;

Collect the production data of the injection-production block, the basic parameters of reservoir physical properties and fluid properties, and use the characteristic expressions obtained from the start-up pressure gradient test experiment, as shown in Table 2:

Table 2 Block statistics

hashtag Permeability Formation thickness Production differential pressure starting pressure gradient crack length Fluid production 1 8.2 12.3 8.2 0.014556 75.6 4.2 2 11.2 8.2 10.4 0.106737 100 7.5 3 14.5 16.5 12.5 0.082552 122.5 15.1 4 15.9 10.2 15.2 0.075318 146 22.3 5 19.8 12.1 11.2 0.060549 132 14.2 6 8.3 26 9.5 0.143815 56.3 4.2 7 10 11.4 13.5 0.119478 124 15.2 8 16 18 15.6 0.074849 130 20.3

The pressure sensitivity coefficient is 0.037 and the viscosity is 1.1mPags

Step 3: Modify the productivity calculation model of vertical well fracturing in low-permeability reservoirs, and obtain the correction factor of the productivity formula through regression training;

The productivity formula of vertical well fracturing in low-permeability reservoirs considering non-Darcy flow is as follows:

Add impact factors β1, β2, β3, β4, and β5 corrections to correct the production capacity formula. The revised capacity formula is as follows:

Substituting the basic data of the reservoir into the revised productivity formula, the equations of the objective function are constructed, and the optimal objective function equations are constructed as follows:

Using the Levenberg-Marquardt optimization iterative method to carry out regression training on the above equations, obtain the influencing factor coefficients β1, β2, β3, β4, β5, and substitute them into the revised production capacity formula, and obtain the production capacity calculation formula matching the target block as follows:

Another set of production data is taken to test the accuracy of the revised capacity formula. The results of the accuracy test are shown in the table below:

Table 3 Accuracy test table

After the accuracy test, the error is <10%, which meets the accuracy requirements, so the production capacity formula is output as the production capacity formula matched with block A.

Step 4: Set the parameter change range, conduct sensitivity analysis, and complete the drawing of the production capacity calculation chart;

Set the variation range of each parameter, and conduct sensitivity analysis on the production capacity formula. Table 4 is the change range of the set parameters and the change table of liquid production.

Table 4 Sensitivity analysis table

Reservoir parameters parameter minimum value maximum value Range of change to sort Permeability value 10 20 4 Fluid production 6.14 6.41 0.26 Formation thickness value 10 15 3 Fluid production 6.14 6.56 0.41 Production differential pressure value 5 10 2 Fluid production 6.14 10.40 4.25 starting pressure gradient value 0 0.05 5 Fluid production 6.14 6.21 0.06 crack half length value 100 150 1 Fluid production 6.14 11.40 5.25

According to the sensitivity experiment, it is determined that the half length of the fracture and the production pressure difference are the two main controlling factors of the productivity of the injection-production unit. The average value of the non-main controlling factors is counted, as shown in Table 5, and the main controlling factors are set as follows: the production pressure difference is set to 5-20MPa, and the half-length of the fracture is set to (10m, 50m, 100m, 150m, 200m).

Table 5 Average parameters of injection-production unit

Based on matlab or excel, draw the production capacity calculation chart of the block, as shown in Figure 4

Step 5: Calculate the balanced water absorption index of the injection well, set different injection-production ratios, and complete the drawing of the water injection pressure chart;

According to the actual production data, the water absorption index is 40m ³ /(dgMPa), and the starting pressure p _c of the water well is 22MPa. Set different injection-production well ratios, and calculate the equilibrium water absorption index under different injection-production well ratios (C), as shown in Table 6:

Table 6 Equilibrium water absorption index table

Ratio of injection and production wells 1:1 1:2 1:3 Equilibrium water absorption index m ³ /(dgMPa) 0.82 1.64 2.46

According to the calculation formula of the water injection volume of the water injection well, the water injection indicator curve is drawn, and the injection characteristic curve under different water injection methods is drawn, as shown in Fig. 5.

The water injection indication curve is superimposed on the productivity calculation chart to form an integrated injection-production chart, as shown in Fig. 6.

Claims (6)

1. it is a kind of consider non-Darcy flow oil reservoir injectivity and productivity plate method for drafting, it is characterised in that comprise the following steps：

Step one：Target block rock core is extracted, test starting barometric gradient obtains feature expression；

Step 2：Oil reservoir basic data is collected, free-boundary problem is calculated；

Step 3：Amendment low-permeability oil deposit vertical well fracture productivity model, regression training obtains the modifying factor of Productivity Formulae；

Step 4：Arrange parameter constant interval, carries out sensitivity analysis, completes the drafting of AOF calculation plate；

Step 5：Water injection well balance injectivity index is calculated, different injection-production ratios are set, complete the drafting of water injection pressure plate.

2. the oil reservoir injectivity and productivity plate method for drafting of non-Darcy flow is considered as claimed in claim 1, it is characterised in that step Rapid one specific method is as follows：

(1) oil reservoir target block, is selected, target block rock core is extracted, after measurement permeability, rock core is soaked；

(2), combine and free-boundary problem experimental apparatus for testing is installed；

(3), slow to fluid is injected in saturated core using high pressure displacement pump, gas column moves feelings in observation port of export capillary Condition, it is determined that minimum start pressure limit；

(4), when in capillary gas column no longer move and when precision instrument reading is constant, recording apparatus pressure value P_g, ask for rock core most Small free-boundary problem；

(5) experimental data after treatment, is made by scatter diagram using computer, and carries out simply data fitting, opened The feature expression of dynamic pressure gradient.

3. as described in claim 1-2 consideration non-Darcy flow oil reservoir injectivity and productivity plate method for drafting, it is characterised in that The specific method of step 2 is as follows：

(1) creation data, reservoir properties, the fluid properties parameter of target block, are collected；

(2), the feature expression obtained using free-boundary problem test experiments, calculates free-boundary problem.

4. as described in claim 1-3 consideration non-Darcy flow oil reservoir injectivity and productivity plate method for drafting, it is characterised in that The specific method of step 3 is as follows：

(1), by adding factor of influence β 1, β 2, β 3, β 4, β 5, low-permeability oil deposit vertical well fracture Productivity Formulae is modified；

(2), by oil reservoir basic data substitution amendment Productivity Formulae, object function equation group is built；

(3) regression training, is carried out to equation group using optimization alternative manner, Productivity Formulae modifying factor is asked for；

(4), the accuracy of the deliverability calculation that test is returned, if not meeting required precision, proceeds to return next time Training, until reaching required precision.

5. as described in claim 1-4 consideration non-Darcy flow oil reservoir injectivity and productivity plate method for drafting, it is characterised in that The specific method of step 4 is as follows：

(1), arrange parameter constant interval, sensitivity analysis is carried out to Productivity Formulae, it is determined that the Dominated Factors of influence block production capacity；

(2) average value of non-Dominated Factors, is counted, the constant interval of Dominated Factors is set；

(3) AOF calculation plate, is drawn.

6. as described in claim 1-5 consideration non-Darcy flow oil reservoir injectivity and productivity plate method for drafting, it is characterised in that The specific method of step 5 is as follows：

(1) the balance injectivity index and water filling for, calculating water injection well start pressure；

(2), different injection-to-producing well ratios are set, the injection indicatrix under different injection mode is drawn；

(3), water injection indication curve and AOF calculation plate are overlapped, note is formed and is adopted integrated plate.