Optimal selection method of water-containing gas reservoir well position

Abstract

The invention belongs to the technical field of well location optimization of dense water-containing gas reservoirs, and particularly relates to a well location optimization method of a water-containing gas reservoir. The method comprises the following seven steps: deploying a well position in a well area, selecting experimental data of a well, calculating the radius of a capillary tube and the thickness of a water film according to the obtained data, calculating irreducible water saturation SWi, calculating movable water saturation SW, judging the result of the calculated SW, and deploying and resuming in the well area where the well position with low water production risk is located. And the water-containing risk of the reservoir is judged through the movable water saturation, so that the water-containing gas reservoir well position is preferably selected in the well area where the well position with the low water production risk is located, the gas-water layer recognition precision is well improved, and the dynamic and static coincidence rate is further improved. By means of the method, geological personnel can conveniently evaluate reservoir analysis, and it is guaranteed that deployment and topdressing are conducted in the well area where the well position with the low water production risk is located.

Description

Technical Field

[0001] The invention belongs to the technical field of tight water-containing gas reservoir well location optimization, and in particular relates to a method for optimizing the well location of a water-containing gas reservoir. Background Art

[0002] The biggest difficulty in optimizing the well location of water-bearing gas reservoirs is how to identify water-bearing gas reservoirs and conduct water-avoiding development. At present, the identification of gas and water layers in the development of water-bearing gas reservoirs at home and abroad mainly relies on seismic and well logging methods. However, since the accuracy of seismic identification of fluids is obviously limited by technology, at this stage, the identification of gas and water layers mainly relies on well logging technology. Since water-bearing gas reservoirs are mainly tight sandstone reservoirs, there is no obvious interface between gas and water, and there is mixed storage of gas and water. The identification accuracy of well logging in water-bearing gas reservoirs is often lower than that of conventional oil and gas reservoirs. It is difficult to improve the current development status of water-bearing gas reservoirs and improve the dynamic and static compliance rate of gas wells.

[0003] At present, the identification of gas-water layers in water-bearing gas reservoirs can be determined by movable water saturation, and the calculation of movable water saturation is often obtained through core fluid experiments. Generally, experiments are time-consuming and require financial support. Summary of the invention

[0004] The present invention provides a method for optimizing well locations in water-containing gas reservoirs. The purpose of the present invention is to address the problems of great difficulty in optimizing well locations in water-containing gas reservoirs, serious water production in producing wells, and low dynamic and static compliance rates. A method for calculating movable water saturation without experimental methods is proposed to quickly evaluate reservoirs so as to implement well location optimization deployment in enrichment areas.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for optimizing well locations of water-bearing gas reservoirs comprises the following steps:

[0007] Step 1: Deploy well locations in the well area;

[0008] Step 2: Select the experimental data of the completed drilling;

[0009] Step 3: Calculate the capillary radius and water film thickness based on the data obtained in step 2;

[0010] Step 4: Calculate bound water saturation S Wi ;

[0011] Step 5: Calculate movable water saturation S W ;

[0012] Step 6: S calculated in step 5 W The results are judged;

[0013] Step 7: Deploy and follow up in the well areas where the wells have low water production risks.

[0014] The experimental data in step 2 include capillary force, pressure difference and liquid viscosity.

[0015] The capillary radius in step 3 is calculated using the following formula:

[0016]

[0017] in:

[0018] θ is the wetting contact angle between fluid and solid;

[0019] p c is the capillary force, unit is MPa;

[0020] r is the capillary radius, in cm;

[0021] σ is the interfacial tension, and its unit is mN / m.

[0022] The water film thickness in step 3 is calculated using the following formula:

[0023] δ=r×0.25763e -0.261r (Δp) -0.419 ×μ w (2)

[0024] in:

[0025] Δp is the pressure difference, in MPa;

[0026] δ is the water film thickness, in nm;

[0027] μ w is the liquid viscosity, the unit is Pa·s.

[0028] In step 4, the bound water saturation S is calculated. Wi The calculation is done using the following method:

[0029]

[0030] Where: N is the effective rock pore volume percentage, %.

[0031] The rock pore volume is calculated as follows:

[0032] According to the capillary bundle model, the rock pore volume Vp is:

[0033]

[0034] in,

[0035] f(r) is the capillary radius distribution frequency, %;

[0036] L(r) is the actual capillary length, in cm;

[0037] r max is the maximum capillary radius, in mm;

[0038] r min is the minimum capillary radius, in mm.

[0039] The capillary length L(r) is obtained by the following method, and the capillary size distribution frequency and tortuosity are described by fractal scaling law:

[0040]

[0041]

[0042]

[0043] in:

[0044] D p is the pore fractal dimension, dimensionless;

[0045] D τ is the fractal dimension of tortuosity, dimensionless;

[0046] L0 is the length of the rock sample, in cm;

[0047] τ is the tortuosity, dimensionless;

[0048] N(r) is the number of capillary radii.

[0049] Step 5 of the present invention is to calculate the movable water saturation S W The process is as follows,

[0050] S W =1-S Wi

[0051] The capillary length L(r) is the product of the length of the rock sample and the tortuosity:

[0052]

[0053] According to formula (5), we get

[0054]

[0055] In the above formula, the pore fractal dimension and tortuosity fractal dimension are:

[0056]

[0057]

[0058] in:

[0059] d is the Euclidean dimension, dimensionless, = 2 in two-dimensional space, = 3 in three-dimensional space;

[0060] φ is porosity, %;

[0061] L O is the length of the rock sample, cm.

[0062] The method for judging the result of irreducible water saturation in step 5; w =50% is the water content boundary of the reservoir, that is, when S w When >50%, the reservoir contains water.

[0063] In the step 7, the well locations are further allocated in the well area where the well locations with low water production risk are located according to 500×650m.

[0064] Beneficial effects:

[0065] (1) The present invention calculates the movable water saturation by fitting the established mathematical model, and uses the movable water saturation to identify the risk of water in the reservoir, so that the well location of the water-containing gas reservoir is preferably in the well area where the well location with low water production risk is located, which greatly improves the accuracy of gas-water layer identification and further improves the dynamic and static consistency rate.

[0066] (2) Through the invented mathematical model formula, by inputting parameters such as the average capillary radius and rock sample tortuosity, the movable water saturation of the well reservoir is calculated, which is convenient for geologists to evaluate reservoir analysis.

[0067] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0069] Figure 1 The present invention is a method flow.

[0070] Figure 2 Schematic diagram of the wetting contact angle between fluid and solid.

[0071] Figure 3 Schematic diagram of the wetting contact angle between fluid and solid is 0°.

[0072] Figure 4 This is a diagram of the occurrence state of bound water in the present invention.

[0073] Figure 5 This is a schematic diagram of the well location deployment of the present invention. DETAILED DESCRIPTION

[0074] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0075] Embodiment 1:

[0076] according to Figure 1 The preferred method for selecting a well location for a water-bearing gas reservoir shown in the figure comprises the following steps:

[0077] Step 1: Deploy well locations in the well area;

[0078] Step 2: Select the experimental data of the completed drilling;

[0079] Step 3: Calculate the capillary radius and water film thickness based on the data obtained in step 2;

[0080] Step 4: Calculate bound water saturation S Wi ;

[0081] Step 5: Calculate movable water saturation S W ;

[0082] Step 6: S calculated in step 5 W The results are judged;

[0083] Step 7: Deploy and follow up in the well areas where the wells have low water production risks.

[0084] In actual use, the present invention determines the risk of water content in the reservoir through the calculation result of movable water saturation, so that the well location of the water-containing gas reservoir is preferably in the well area where the well location with low water production risk is located, which greatly improves the accuracy of gas-water layer identification and further improves the dynamic and static consistency rate.

[0085] Embodiment 2:

[0086] according to Figure 1-Figure 4 The preferred method for selecting a well location for a water-bearing gas reservoir shown in the embodiment is different from that of the first embodiment in that the experimental data in the second step includes capillary force, pressure difference and liquid viscosity.

[0087] In actual use, when the reservoir is strongly hydrophilic θ = 0°, it is clear that the bound water is mainly the film bound water retained on the large pore wall due to the molecular force on the surface of the hydrophilic rock. Due to differences in pore structure, displacement pressure difference, gas-water properties, etc., the bound water saturation is variable. The calculation methods of the critical capillary radius and the bound water film thickness are:

[0088]

[0089] δ=r×0.25763e -0.261r (Δp) -0.419 ×μ w (2)

[0090] in:

[0091] θ is the wetting contact angle between fluid and solid;

[0092] p c is the capillary force, unit is MPa;

[0093] r is the capillary radius, in cm;

[0094] σ is the interfacial tension, in mN / m;

[0095] Δp is the pressure difference, in MPa;

[0096] δ is the water film thickness, in nm;

[0097] μ w is the liquid viscosity, the unit is Pa·s.

[0098] The viscosity of the water phase is mainly affected by temperature, and the effect of pressure is very small and can be ignored. Therefore, the thickness of the water film is mainly controlled by the capillary radius, pressure difference and temperature.

[0099] According to the capillary bundle model, the rock pore volume is:

[0100]

[0101] The total volume of bound water V can be obtained from the critical capillary radius and the bound water film thickness: w for:

[0102]

[0103] in,

[0104] f(r) is the capillary radius distribution frequency, in %;

[0105] L(r) is the actual capillary length in cm.

[0106] Immune water saturation is:

[0107]

[0108] The capillary size distribution frequency and tortuosity can be described by fractal scaling laws:

[0109]

[0110]

[0111]

[0112] in:

[0113] D p is the pore fractal dimension, dimensionless;

[0114] D τ is the fractal dimension of tortuosity, dimensionless;

[0115] L0 is the length of the rock sample, in cm;

[0116] τ is the tortuosity, unit is dimensionless;

[0117] N(r) is the number of capillary radii.

[0118] The capillary length L(r) is the product of the length of the rock sample and the tortuosity:

[0119]

[0120]

[0121] Among them, the pore fractal dimension and tortuosity fractal dimension are:

[0122]

[0123]

[0124] in:

[0125] d is the Euclidean dimension, dimensionless, = 2 in two-dimensional space, = 3 in three-dimensional space;

[0126] φ is porosity, %;

[0127] L O is the length of the rock sample, cm.

[0128] Usually S w =50% is the water content boundary of the reservoir, that is, when S w When >50%, the reservoir contains water.

[0129] According to the obtained S wIn the well areas where the water production risk is low, the well locations are expanded according to 500×650m.

[0130] The present invention proposes a method for rapidly evaluating reservoirs and optimizing well locations in enriched areas by calculating movable water saturation instead of conducting experiments, and the dynamic and static conformity rates are relatively high.

[0131] Embodiment three:

[0132] Reference Figure 5 , a specific application example of a method for optimizing well locations in water-containing gas reservoirs.

[0133] For the wells X1 and X2 that have been drilled in a certain study area, the known relevant parameters are shown in Table 1.

[0134] Table 1 Comparison of model and experimental results

[0135]

[0136] 2. Substitute the relevant parameters into formula 10.

[0137] Well X1: Sw = 1-S Wi =1-56.7%=43.6%

[0138] Well X2: Sw = 1-S Wi =1-46.1%=53.9%

[0139] Among them, SW i is the bound water saturation.

[0140] When Sw>50%, the reservoir contains water.

[0141] The water production risk of well X2 is high, so the well area where well X1 is located is selected for well site deployment and follow-up.

[0142] In the absence of conflicts, technicians in this field can combine the relevant technical features in the above examples according to actual conditions to achieve corresponding technical effects. The specific combinations are not described here one by one.

[0143] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0144] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0145] The above are only preferred embodiments of the present invention. The present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing well locations of water-bearing gas reservoirs, characterized in that: The steps include: Step 1: Deploy well locations in the well area; Step 2: Select the experimental data of the completed drilling; Step 3: Calculate the capillary radius and water film thickness based on the data obtained in step 2; Step 4: Calculate bound water saturation S Wi ; Step 5: Calculate movable water saturation S W ; Step 6: S calculated in step 5 W The results are judged; Step 7: Deploy and follow up in the well areas where the wells have low water production risks.

2. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: The experimental data in step 2 include capillary force, pressure difference and liquid viscosity.

3. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: The capillary radius in step 3 is calculated using the following formula: in: θ is the wetting contact angle between fluid and solid; p c is the capillary force, unit is MPa; r is the capillary radius, in cm; σ is the interfacial tension, and its unit is mN / m.

4. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: The water film thickness in step 3 is calculated using the following formula: δ=r×0.25763e -0.261r (Δp) -0.419 ×m w (2) in: Δp is the pressure difference, in MPa; δ is the water film thickness, in nm; μ w is the liquid viscosity, the unit is Pa·s.

5. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: In step 4, the bound water saturation S is calculated. Wi The calculation is done using the following method: Where: N is the effective rock pore volume percentage, %.

6. The method for optimizing the well location of a water-bearing gas reservoir according to claim 5, characterized in that: The rock pore volume is calculated as follows: According to the capillary bundle model, the rock pore volume Vp is: in, f(r) is the capillary radius distribution frequency, %; L(r) is the actual capillary length, in cm; r max is the maximum capillary radius, in mm; r min is the minimum capillary radius, in mm.

7. The method for optimizing the well location of a water-bearing gas reservoir according to claim 6, characterized in that: The capillary length L(r) is obtained by the following method: The capillary size distribution frequency and tortuosity are described by fractal scaling laws: in: D p is the pore fractal dimension, dimensionless; D τ is the fractal dimension of tortuosity, dimensionless; L0 is the length of the rock sample, in cm; τ is the tortuosity, dimensionless; N(r) is the number of capillary radii.

8. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: Step 5 of the present invention is to calculate the movable water saturation S W The process is as follows, S W =1-S Wi The capillary length L(r) is the product of the length of the rock sample and the tortuosity: According to formula (5), we get In the above formula, the pore fractal dimension and tortuosity fractal dimension are: in: d is the Euclidean dimension, dimensionless, = 2 in two-dimensional space, = 3 in three-dimensional space; φ is porosity, %; L O is the length of the rock sample, cm.

9. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: The method for judging the result of irreducible water saturation in step 5; w =50% is the water content boundary of the reservoir, that is, when S w When >50%, the reservoir contains water.

10. The method for optimizing the well location of a water-bearing gas reservoir according to claim 1, characterized in that: In the step 7, the well locations are further distributed in the well area where the well locations with low water production risk are located according to 500×650m.

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