CN112257349B - Method for judging whether tight sandstone movable water-gas reservoir gas well has development value - Google Patents
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Abstract
The invention provides a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value or not, which considers the effective gas-phase permeability k of movable water in the reservoir g Formation fluid integrated viscosity
And a flow boundary r e And three influencing factors are used for establishing a compact sandstone water-bearing gas reservoir gas well productivity calculation formula, so that the gas well productivity can be accurately calculated. According to the method, through the combination of indoor tests and practical application, an effective permeability empirical formula is established when the test rock core and the block have the stratum movable water, the reutilization of the experimental data of the rock core in the tight sandstone water-containing gas reservoir is expanded, the gas well productivity of the gas reservoir and the influence factors and the change rule thereof are evaluated scientifically and reasonably, the influence degree of the stratum movable water on the productivity under different reservoir conditions can be evaluated rapidly, and the reasonable production allocation and the reasonable development technical policy of the tight sandstone water-containing gas reservoir are facilitated.
Description
Technical Field
The invention belongs to the technical field of gas reservoir engineering, and particularly relates to a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value.
Background
The tight sandstone water-containing gas reservoir occupies a great position in natural gas reserves, the large-scale benefit development of the water-containing gas reservoir faces a great technical challenge, and the accurate calculation of the productivity of the tight sandstone water-containing gas reservoir gas well has very important significance for long-term stable production of the water-producing gas well and fine management of the gas well. The related technologies of the existing method for evaluating the productivity of the gas well of the tight sandstone water-containing gas reservoir comprise tight sandstone water-containing gas reservoir seepage mechanism experiments, theoretical model researches, a tight sandstone gas reservoir low-speed nonlinear abortion energy formula and the like.
The conventional evaluation method has a larger problem, the main problem of the seepage mechanism experimental technology is that the visualization experiment of a real core slice reveals the gas-water distribution change rule in the gas-water displacement process, although the permeability of a sample is also measured, the two-dimensional rock slice cannot obtain the influence rule of different water saturation on the effective permeability, in addition, the wettability of a glass partition plate in a visualization model is different from that of the actual stratum rock, and the influence of the wettability of a pore passage of a compact reservoir on the seepage rule is very obvious; the CT scanning digital core technology is expensive in cost, is limited by scanning precision and resolution, and has great limitation on the pore structure simulation function of the compact reservoir rock; a power function type empirical formula of the starting pressure gradient, the absolute permeability and the water saturation of the rock core is established according to the high-precision rock core test, but the power function type empirical formula is not consistent with an internationally recognized exponential function that the starting pressure gradient is fluidity. For the problems existing in the productivity formula of the low-speed nonlinear seepage theory, most researches are only limited to adding a starting pressure gradient in a mathematical model, stress sensitivity and slip effect are considered through a coefficient term, but the influence rule of movable water on the formation flow capacity is not considered from the angle of influencing the nonlinear seepage characteristic; the influence of the boundary layer in the microchannel on the seepage rule can be considered in part of more complex theoretical models, and the influence of stress sensitivity, a slip effect, a starting pressure gradient, movable water saturation and the like on the seepage rule can be considered, but the parameters required by the models are often difficult to obtain completely and the solution is difficult.
The existence of movable water aggravates the nonlinear seepage characteristic of tight sandstone gas reservoir rock, obviously reduces the flowing capacity of the rock, and has great influence on the gas well productivity, the stable production capacity, the gas sand recovery ratio and the like. The method has the advantages that the influence degree of the productivity of the gas well of the water-tight sandstone gas reservoir and the stratum yielding water on the productivity of the gas well is evaluated scientifically and reasonably, and the optimization of the gas well production allocation and field development strategies is facilitated.
Disclosure of Invention
The invention aims to provide a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value or not, and the technical problems in the prior art are solved.
Therefore, the invention provides a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value, which comprises the following steps:
step 1) obtaining the gas well productivity q sc And the movable water saturation degree S wm The relational expression of (1);
step 2) let the movable water saturation S wm Is 0, according to gas well productivity q sc And movable water saturation degree S wm To obtain the gas well productivity q sc0 ；
Step 3) calculating the saturation S of each movable water wm Corresponding gas well productivity q sc By q sc /q sc0 Obtaining the productivity retention rate;
step 4) obtaining movable water saturation S wm A graph of productivity retention rate;
step 5) when the movable water saturation S wm And when the productivity retention rate is more than 15% and less than 0.2, judging that the gas reservoir gas well has no development value.
Step 1) the gas well productivity q sc And the movable water saturation degree S wm Is to take into account the gas phase effective permeability k of mobile water within the reservoir g Comprehensive viscosity of formation fluid
And a flow boundary r e Three influencing factors are obtained.
Step 1) obtaining the productivity q of the gas well sc And movable water saturation degree S wm The specific process of the relation (c) is as follows:
(1) Obtaining the gas phase effective permeability k of the rock according to the gas-water flow test data of the rock core g And the movable water saturation degree S wm Absolute permeability k ∞ The relational expression of (1);
(2) According to the viscosity of natural gas under the average pressure of stratum
Formation water viscosity mu w And movable water saturation degree S wm Obtaining the comprehensive viscosity of the formation fluid under the formation condition
(3) Establishing a flow boundary r e Flow pressure p along with the bottom of the well w The variation relation of (1);
(4) According to the effective permeability k of the rock in the gas phase g Comprehensive viscosity of formation fluid
And a flow boundary r e Establishing a compact sandstone water-bearing gas reservoir gas well productivity calculation formula to obtain the gas well productivity q sc And movable water saturation degree S wm The relational expression (c) of (a).
The step (1) is to combine the gas phase effective permeability k of the rock under different movable water saturation conditions of the rock core g Regression to establish different absolute permeabilities k ∞ And movable water saturation S wm The following empirical formula for effective permeability:
k g ＝k ∞ ·k rg (S wm )
in the formula, k ∞ Is the rock absolute permeability, mD; k is a radical of rg (S wm ) As movable water saturation S wm And permeability retention rate k rg The relational expression (c) of (a).
Step (2) is carried out by measuring the viscosity of the natural gas under the average pressure of the stratum
Viscosity mu with formation water w Movable water saturation S wm Weighting to obtain the comprehensive viscosity of the formation fluid
In the formula (I), the compound is shown in the specification,
viscosity of natural gas, cP, at the average pressure of the formation; mu.s w Formation water viscosity, cP;
is the formation fluid integrated viscosity, cP; s wm Is the formation mobile water saturation.
Step (3) is to establish a flow boundary r based on the radial flow stratum pressure distribution and the starting pressure gradient, the gas well production pressure difference, the seepage characteristic and the fluid parameter e Flow pressure p along with bottom hole w The variation relation of (c);
in the formula, p w Is the bottom hole flowing pressure, MPa; p is a radical of i Is the formation static pressure, MPa; k is a radical of g Is the gas phase effective permeability, mD, of the rock;
is the formation fluid integrated viscosity, cP.
Step (3) gas well productivity q sc And movable water saturation degree S wm The relationship of (a) is as follows:
in the formula, q sc For gas well production, m 3 /d；k g Is the gas phase effective permeability, mD, of the reservoir rock; h is the effective thickness of the reservoir, m; p is a radical of i Is the formation static pressure, MPa; p is a radical of formula w Is bottom hole flowing pressure, MPa; t isFormation temperature, K;
is the formation fluid integrated viscosity, cP;
is the average formation natural gas eccentricity factor; r is a radical of hydrogen e Is the gas well flow boundary, m; r is w Is the gas well borehole radius, m; s is the epidermal coefficient; s wm Is the formation mobile water saturation.
Local formation pressure gradient g ri When the starting pressure gradient lambda is not exceeded, the corresponding distance r b Is the flow boundary r corresponding to the bottom hole pressure e ：
In the formula, r b Is the radial distance, m, of the gas well flow boundary; g ri Is the formation pressure gradient, m; λ is the starting pressure gradient, m.
The invention has the beneficial effects that:
the method for judging whether the gas well of the tight sandstone movable water-gas reservoir has development value or not is implemented by considering the effective gas-phase permeability k of the movable water in the reservoir g Comprehensive viscosity of formation fluid
And a flow boundary r e And three influencing factors are used for establishing a compact sandstone water-bearing gas reservoir gas well productivity calculation formula, so that the gas well productivity can be accurately calculated.
According to the method, through the combination of indoor tests and practical application, an effective permeability empirical formula is established when the test rock core and the block have stratum movable water, the reutilization of the experimental data of the rock core in the tight sandstone water-containing gas reservoir chamber is expanded, the gas well productivity of the gas reservoir and the influence factors and the change rule of the gas well productivity are evaluated scientifically and reasonably, and the reasonable production allocation and the reasonable development technical policy of the tight sandstone water-containing gas reservoir are facilitated.
The method can quickly evaluate the influence degree of the stratum movable water on the productivity under different reservoir conditions.
This will be described in further detail below with reference to the accompanying drawings.
Drawings
FIG. 1 is a graph of movable water saturation versus permeability retention for 51 well 2-1/125 cores in an example of the present invention;
FIG. 2 is a graph of movable water saturation versus permeability retention for a x73 well 3-17/44 core in an example of the invention;
FIG. 3 is a graph of movable water saturation versus permeability retention for a x29 well 2-5/133 core in an example of the invention;
FIG. 4 is a graph of movable water saturation versus permeability retention for x124 wells 5-13/47 cores in an example of the present invention;
FIG. 5 is a graph of the effect of mobile water saturation on capacity retention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their context in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Example 1:
the embodiment provides a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value, which comprises the following steps:
step 1) obtaining the gas well productivity q sc And the movable water saturation degree S wm The relational expression of (1);
step 2) let the movable water saturation S wm Is 0, according to gas well productivity q sc And the movable water saturation degree S wm To obtain the gas well productivity q sc0 ；
Step 3) calculating the saturation S of each movable water wm Corresponding gas well productivity q sc By q sc /q sc0 Obtaining the productivity retention rate;
step 4) obtaining movable water saturation S wm A graph relating to productivity retention;
step 5) when the movable water saturation S wm And when the productivity retention rate is more than 15% and less than 0.2, judging that the gas reservoir gas well has no development value.
The method helps to reasonably allocate the production and establish a reasonable development technical policy of the compact sandstone water-containing gas reservoir by researching the influence of the dynamic water saturation on the productivity conservation rate.
Example 2:
on the basis of embodiment 1, the embodiment provides a method for judging whether a tight sandstone movable water gas reservoir gas well has development value, and the gas well productivity q) in the step 1) is sc And movable water saturation degree S wm Is given by the gas phase effective permeability k of the mobile water in the reservoir g Comprehensive viscosity of formation fluid
And a flow boundary r e Three influencing factors are obtained.
This example establishes a gas phase effective permeability k that takes into account mobile water within the reservoir g Comprehensive viscosity of formation fluid
And a flow boundary r e Compact sandstone under three influencing factorsThe productivity calculation formula of the water-bearing gas reservoir gas well effectively solves the problems that the existing gas well productivity evaluation method is complex and inaccurate in calculation, and can achieve the purpose of quickly calculating the productivity of the tight sandstone water-bearing gas reservoir gas well.
Example 3:
on the basis of the embodiment 1 or 2, the embodiment provides a method for judging whether the tight sandstone movable water-gas reservoir gas well has development value, and the step 1) obtains the gas well productivity q sc And movable water saturation degree S wm The specific process of the relation (c) is as follows:
(1) Obtaining the effective gas-phase permeability k of the rock according to the gas-water flow test data of the rock core g And the movable water saturation degree S wm Absolute permeability k ∞ The relational expression of (1);
(2) According to the viscosity of natural gas under the average pressure of stratum
Formation water viscosity mu w And the movable water saturation degree S wm Obtaining the comprehensive viscosity of the formation fluid under the formation condition
(3) Establishing a flow boundary r e Flow pressure p along with bottom hole w The variation relation of (1);
(4) According to the gas phase effective permeability k of the rock g Formation fluid integrated viscosity
And a flow boundary r e Establishing a compact sandstone water-bearing gas reservoir gas well productivity calculation formula to obtain the gas well productivity q sc And the movable water saturation degree S wm The relational expression (c) of (c).
The method combines the indoor test with the practical application, expands the reutilization of the indoor core test data of the tight sandstone water-containing gas reservoir, establishes the effective permeability empirical formula when the test core and the block have the stratum movable water, and scientifically and reasonably evaluates the gas well productivity of the gas reservoir, the influence factors and the change rule thereof. The gas well productivity equation considers nonlinear influence factors such as movable water, a flow boundary and the like, and the calculation result is more accurate.
Example 4:
on the basis of embodiment 3, the embodiment provides a method for judging whether a tight sandstone movable water gas reservoir gas well has development value, and the step (1) is to combine the effective gas phase permeability k of the rock under the conditions of different movable water saturations of the rock core g Regression establishes different absolute permeabilities k ∞ And movable water saturation S wm The following empirical formula for effective permeability:
k g ＝k ∞ ·k rg (S wm )
in the formula, k ∞ Is the rock absolute permeability, mD; k is a radical of formula rg (S wm ) As movable water saturation S wm And permeability retention rate k rg The relational expression (c) of (c).
For a compact water-containing gas reservoir, certain initial movable water is contained in a pore network space, the gas phase permeability is obviously influenced by the movable water saturation, and an empirical formula of the effective permeability under different absolute permeability and movable water saturation is established by regression by combining effective permeability and starting pressure gradient test data of a rock core under different movable water saturation conditions.
Example 5:
on the basis of the embodiment 3, the embodiment provides a method for judging whether the tight sandstone movable water-gas reservoir gas well has development value, and the step (2) is to determine the viscosity of the natural gas under the average pressure of the stratum
Viscosity mu with formation water w Degree of movable water saturation S wm Weighting to obtain the comprehensive viscosity of the formation fluid
In the formula (I), the compound is shown in the specification,
viscosity of natural gas, cP, at the average pressure of the formation; mu.s w Formation water viscosity, cP;
is the formation fluid integrated viscosity, cP; s. the wm Is the formation mobile water saturation.
For dense water-bearing reservoirs, the formation fluid comprises natural gas and formation mobile water, and although the saturation of the mobile water is very low, the apparent viscosity of the gas-water two-phase flow will be significantly affected by the presence of the mobile water, since the viscosity of water is much higher than that of natural gas. Thus for a tight water-bearing reservoir, the average viscosity of the formation fluid should be weighted by the natural gas viscosity at the average pressure of the formation and the saturation of the formation water viscosity:
example 6:
on the basis of embodiment 3, the embodiment provides a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value, and the step (3) is to establish a flow boundary r based on radial flow formation pressure distribution and starting pressure gradient, gas well production pressure difference, seepage characteristics and fluid parameters e Flow pressure p along with the bottom of the well w The variation relation of (c);
in the formula, p w Is bottom hole flowing pressure, MPa; p is a radical of formula i Static formation pressure, MPa; k is a radical of formula g Is the gas phase effective permeability, mD, of the rock;
is the formation fluid integrated viscosity, cP.
The method comprises the steps of enabling a compact water-containing gas reservoir to have a remarkable starting pressure effect, enabling each production pressure difference to correspond to a flow boundary, enabling the flow boundary of a gas well to be the actual control radius of the gas well, enabling the production pressure difference and the formation flow capacity to be main control factors of the control radius of the gas well, and establishing a change relation of the flow boundary along with the bottom hole flow pressure by combining the production pressure difference, the seepage characteristics and fluid parameters of the gas well.
Example 7:
on the basis of embodiment 3, the embodiment provides a method for judging whether a tight sandstone movable water-gas reservoir gas well has development value, and step (3) the gas well productivity q sc And the movable water saturation degree S wm The relationship of (A) is as follows:
in the formula, q sc For gas well production, m 3 /d；k g Is the gas phase effective permeability, mD, of the reservoir rock; h is the effective thickness of the reservoir, m; p is a radical of formula i Static formation pressure, MPa; p is a radical of formula w Is bottom hole flowing pressure, MPa; t is the formation temperature, K;
is the formation fluid integrated viscosity, cP;
is the average formation natural gas eccentricity factor; r is e Is the gas well flow boundary, m; r is a radical of hydrogen w Is the gas well borehole radius, m; s is the epidermal coefficient; s. the wm Is the formation mobile water saturation.
For the compact water-containing gas reservoir, the influence of movable water on gas phase permeability, comprehensive viscosity of formation fluid and gas well control range must be considered, and based on the evaluation of the influence factors, a gas well productivity formula of the compact water-containing gas reservoir is established.
Wherein k is g ＝k ∞ ·k rg (S wm )，
To obtain the following formula:
k rg (S wm ) As movable water saturation S wm And permeability retention rate k rg The permeability retention rate is the gas phase effective permeability k g Absolute permeability k of rock ∞ The ratio of (a) to (b).
Example 8:
on the basis of the embodiment 1 or 2 or 3 or 4 or 5 or 6 or 7, the embodiment provides a method for judging whether the tight sandstone movable water-gas reservoir gas well has development value, which specifically comprises the following steps:
step one, combining core gas-water flow test data to establish an effective permeability empirical formula
For a compact water-containing gas reservoir, certain initial movable water is contained in a pore network space, the gas phase permeability is obviously influenced by the movable water saturation, and an empirical formula of the effective permeability under different absolute permeability and movable water saturation is established by regression by combining effective permeability and starting pressure gradient test data under different movable water saturation conditions of a rock core:
k g ＝k ∞ ·k rg (S wm )
step two, establishing the viscosity of the formation fluid under the formation condition
For dense water-bearing reservoirs, the formation fluids include natural gas and formation mobile water, and although the mobile water is very low in saturation, the apparent viscosity of the gas-water two-phase flow will be significantly affected by the presence of the mobile water, since the viscosity of water is much higher than that of natural gas. Thus for a tight water-bearing reservoir, the average viscosity of the formation fluid should be weighted by the viscosity of the natural gas at the average pressure of the formation and the saturation of the formation water viscosity:
step three, based on the pressure distribution of the radial flow stratum and the starting pressure gradient, calculating the flow boundary under each bottom hole flow pressure
The method comprises the following steps of (1) establishing a change relation formula of a flow boundary along with the bottom flowing pressure by combining the production pressure difference, the seepage characteristic and the fluid parameter of the gas well, wherein the compact water-containing gas reservoir has a remarkable starting pressure effect, each production pressure difference corresponds to one flow boundary, the flow boundary of the gas well is the actual control radius of the gas well, the production pressure difference and the formation flowing capacity are main control factors of the control radius of the gas well, and the change relation formula of the flow boundary along with the bottom flowing pressure of the gas well is established:
step four, establishing a tight sandstone water-bearing gas reservoir gas well productivity calculation formula
For the compact water-containing gas reservoir, the influence of movable water on gas phase permeability, comprehensive viscosity of formation fluid and gas well control range must be considered, and based on the evaluation of the influence factors, a gas well productivity formula of the compact water-containing gas reservoir is established.
In the formula: q. q.s sc For gas well production, m 3 /d；k g Is the gas phase effective permeability, mD, of the reservoir rock; h is the effective thickness of the reservoir, m; p is a radical of formula i Is the formation static pressure, MPa; p is a radical of w Is the bottom hole flowing pressure, MPa; t is the formation temperature, K;
is the formation fluid integrated viscosity, cP;
is the average formation natural gas eccentricity factor; r is e Is the gas well flow boundary, m; r is w Is the gas well borehole radius, m; s is the epidermal coefficient; s wm Formation mobile water saturation;
viscosity of natural gas, cP, at the average pressure of the formation; mu.s w Is the formation water viscosity, cP.
The flow boundary calculation principle in the third step is as follows:
the production pressure drop will create a near-to-far pressure drop funnel in the formation, within which the formation pressure at various locations is proportional to the logarithm of the radial distance, i.e.:
in the formula: p is a radical of formula e The formation pressure at the boundary of the well control range is MPa; p is the formation pressure at any radial distance r, MPa; r is any radial distance, m.
Calculating the formation pressure at each radial distance: p is a radical of formula ri I =0,1,2,. Cndot, n, wherein:
p r0 ＝p w ,p rn ＝p e
calculating the formation pressure gradient at each radial distance: g is a radical of formula ri I =1, 2.., n, wherein:
g ri ＝(p ri -p ri-1 )/(r i -r i-1 )
and the radial distance is from near to far, and when the formation pressure gradient does not exceed the starting pressure gradient, the corresponding distance is the flow boundary corresponding to the bottom hole pressure:
in the formula: r is b Is the radial distance, m, of the gas well flow boundary; g is a radical of formula ri Is the formation pressure gradient, m.
Well control range r e The inner reserves are single well geological reserves and the actual stratum flow range r under the current bottom hole pressure b The reservoir in (c) is the single well recoverable reservoir (assuming the current bottom-hole pressure is higher than the abandoned bottom-hole pressure) from which the gas well recovery is estimated. At this time, the flow boundary r e Take a value of r b 。
Example 9:
this example illustrates the present invention in further detail by taking a block in a tight sandstone reservoir as an example.
Performing a plurality of groups of core flow test tests on a block in the tight sandstone water-bearing gas reservoir, wherein the original formation pressure p of the block i 33.5MPa, formation water viscosity, mu w Viscosity of natural gas at formation mean pressure of 0.28cP
Is 1.2656 × 10 -2 cP。
1. Collecting the block test data and establishing the effective permeability empirical formula of the zone
Four cores of 51 wells 2-1/125 core, x73 wells 3-17/44 core, x29 wells 2-5/133 core and x124 wells 5-13/47 core are respectively selected, and the effective permeability experimental data are shown in table 1.
Table 1 effective permeability experimental data
And (3) according to effective permeability test data of the 4 rock samples with different water saturations, regressing empirical formulas of water saturation and permeability retention rate (gas phase effective permeability/rock absolute permeability), and respectively showing the empirical formulas in figures 1,2, 3 and 4.
And (3) according to effective permeability test data of the 4 rock samples in the block under different water saturation degrees, regressing an empirical formula of effective permeability to obtain an empirical formula of the ratio of the effective permeability to the absolute permeability of the compact reservoir in the block under the condition that movable water exists:
2. establishing an empirical formula of the viscosity of the formation fluid under the formation conditions of the block
Combining the block dynamic monitoring data to obtain the horizontal average viscosity of the natural gas and the stratum, and establishing a stratum fluid viscosity empirical formula of a natural gas and movable water coexisting system under the stratum condition according to saturation weighting:
3. establishing the block gas well flow boundary calculation empirical formula
1) The calculation principle is as follows: the production pressure drop will create a near-to-far pressure drop funnel in the formation, within which the formation pressure at each location is proportional to the logarithm of the radial distance, i.e.:
in the formula: p is a radical of formula e The formation pressure at the boundary of the well control range is MPa; p is a radical of w Is bottom hole flowing pressure, MPa; p is the formation pressure at any radial distance r, MPa; r is w Is the gas well borehole radius, m; r is e Is the gas well flow boundary (radial distance of well control range boundary), m; r is any radial distance, m.
Calculating the formation pressure at each radial distance: p is a radical of ri I =0,1,2, ·, n, wherein:
p r0 ＝p w ,p rn ＝p e
calculating the formation pressure gradient at each radial distance: g ri I =1,2, n, wherein:
g ri ＝(p ri -p ri-1 )/(r i -r i-1 )
and the radial distance is from near to far, and when the formation pressure gradient does not exceed the starting pressure gradient, the corresponding distance is the flow boundary corresponding to the bottom hole pressure:
in the formula: r is b Is the radial distance, m, of the gas well flow boundary; g is a radical of formula ri Is the formation pressure gradient, m.
Well control range r e The inner reserves are single well geological reserves and the actual stratum flow range r under the current bottom hole pressure b The reservoir in (c) is the single well recoverable reservoir (assuming the current bottom-hole pressure is higher than the abandoned bottom-hole pressure) from which the gas well recovery is estimated.
2) Block example calculation: the absolute permeability of the reservoir rock in the block is 0.1-2.5 mD, the movable water saturation is about 0.2 at most, and three bottom hole flow pressures of 7.5 MPa, 5.0 MPa and 2.5MPa are set. Gas well flow boundaries are calculated from the combination of parameters, as shown in table 2:
obtaining an empirical formula of the flow boundary of the gas well in the work area by using a multiple regression analysis method:
the data show that formation water production has a significant effect on the flow boundaries of gas wells. The gas well flow boundary decreases rapidly at the initial water production, but gradually diminishes as the formation is further produced. The reservoir formation research shows that the compact gas reservoir contains more water, and the occurrence of movable water in the middle and later periods of production is inevitable, so that the influence of formation effluent is required to be considered during capacity evaluation and development scheme preparation.
4. Establishing a productivity calculation equation of the block gas well
Based on gas-water flow experimental data of reservoir rock samples in the work area, combining with a seepage mechanics theoretical model, and according to the empirical formulas of the three influence factors, obtaining a gas well productivity calculation formula suitable for the reservoir in the block:
according to the obtained calculation formula of the productivity of the gas well in the block, the yield of the gas well (or the unobstructed flow of the gas well) under the combination of typical reservoir and fluid parameters of the work area is calculated, as shown in the table 3:
TABLE 3 calculation data table for gas well non-resistance flow in work area
The statistical calculation results show that the amplitude of the gas well production energy is reduced remarkably by the formation water, and the influence rule is shown in figure 5. Therefore, for dynamic water saturation S wm And if the productivity retention rate is more than 15% and less than 0.2, judging that the gas well has no development value.
The above examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention, which is intended to be covered by the claims and any design similar or equivalent to the scope of the invention.
Claims (8)
1. A method for judging whether a tight sandstone movable water-gas reservoir gas well has development value is characterized by comprising the following steps:
step 1) obtaining the gas well productivity q sc And the movable water saturation degree S wm The relational expression of (a);
step 2) let the movable water saturation S wm Is 0, according to gas well productivity q sc And movable water saturation degree S wm To obtain the gas well productivity q sc0 ；
Step 3) calculating the saturation S of each movable water wm Corresponding gas well productivity q sc By q sc /q sc0 Obtaining the productivity retention rate;
step 4) obtaining movable water saturation S wm Koji with productivity retention rateLine drawing;
step 5) when the movable water saturation S wm And when the productivity retention rate is more than 15% and less than 0.2, judging that the gas reservoir gas well has no development value.
2. The method for judging whether the tight sandstone mobile water-gas reservoir gas well has development value or not according to claim 1, wherein the gas well productivity q in the step 1) is sc And movable water saturation degree S wm Is to take into account the gas phase effective permeability k of mobile water within the reservoir g Comprehensive viscosity of formation fluid
And a flow boundary r e Three influencing factors are obtained.
3. The method for judging whether the tight sandstone movable water-gas reservoir gas well has development value or not according to claim 1 or 2, wherein the step 1) is used for obtaining the yield q of the gas well sc And movable water saturation degree S wm The specific process of the relation of (1) is as follows:
(1) Obtaining the gas phase effective permeability k of the rock according to the gas-water flow test data of the rock core g And movable water saturation degree S wm Absolute permeability k ∞ The relational expression of (1);
(2) According to the viscosity of natural gas under the average pressure of stratum
Formation water viscosity mu w And movable water saturation degree S wm Obtaining the comprehensive viscosity of the formation fluid under the formation condition
(3) Establishing a flow boundary r e Flow pressure p along with the bottom of the well w The variation relation of (1);
(4) According to the gas phase effective permeability k of the rock g Formation fluid integrated viscosity
And a flow boundary r e Establishing a compact sandstone water-bearing gas reservoir gas well productivity calculation formula to obtain the gas well productivity q sc And the movable water saturation degree S wm The relational expression (c) of (c).
4. The method for judging whether the tight sandstone mobile water-gas reservoir gas well has development value or not according to claim 3, wherein the method comprises the following steps: the step (1) is to combine the gas phase effective permeability k of the rock under different movable water saturation conditions of the rock core g Regression establishes different absolute permeabilities k ∞ And movable water saturation S wm The following empirical formula for effective permeability:
k g ＝k ∞ ·k rg (S wm )
in the formula, k ∞ Is the rock absolute permeability, mD; k is a radical of rg (S wm ) As movable water saturation S wm And permeability retention rate k rg The relational expression (c) of (c).
5. The method for judging whether the tight sandstone mobile water-gas reservoir gas well has development value or not according to claim 3, wherein the method comprises the following steps: step (2) is carried out by measuring the viscosity of the natural gas under the average pressure of the stratum
Viscosity mu with formation water w Degree of movable water saturation S wm Weighting to obtain the comprehensive viscosity of the formation fluid
In the formula (I), the compound is shown in the specification,
viscosity of natural gas, cP, at the average pressure of the formation; mu.s w Formation water viscosity, cP;
is the formation fluid integrated viscosity, cP; s wm Is the formation mobile water saturation.
6. The method for judging whether the tight sandstone mobile water-gas reservoir gas well has development value or not according to claim 3, wherein the method comprises the following steps: step (3) is based on the radial flow stratum pressure distribution and the starting pressure gradient, the gas combination well production pressure difference, the seepage characteristic and the fluid parameter to establish a flow boundary r e Flow pressure p along with the bottom of the well w The variation relation of (c);
in the formula, p w Is bottom hole flowing pressure, MPa; p is a radical of formula i Static formation pressure, MPa; k is a radical of g Is the gas phase effective permeability, mD, of the rock;
is the formation fluid integrated viscosity, cP.
7. The method for judging whether the tight sandstone mobile water gas reservoir gas well has development value or not according to claim 3, wherein the method comprises the following steps: step (3) gas well productivity q sc And the movable water saturation degree S wm The relationship of (A) is as follows:
in the formula, q sc For gas well production, m 3 /d；k g Is the gas phase effective permeability of the reservoir rock, mD; h is the effective thickness of the reservoir, m; p is a radical of i In order to obtain the static pressure of the stratum,MPa；p w is the bottom hole flowing pressure, MPa; t is the formation temperature, K;
is the formation fluid integrated viscosity, cP;
is the mean formation gas eccentricity factor; r is e Is the gas well flow boundary, m; r is w Is the gas well borehole radius, m; s is the epidermal coefficient; s. the wm Is the formation mobile water saturation.
8. The method for judging whether the tight sandstone mobile water-gas reservoir gas well has development value or not according to claim 3, wherein the method comprises the following steps: local formation pressure gradient g ri When the starting pressure gradient lambda is not exceeded, the corresponding distance r b Is the flow boundary r corresponding to the bottom hole pressure e ：
r b ＝r| gri≤λ
In the formula, r b Is the radial distance, m, of the gas well flow boundary; g ri Is the formation pressure gradient, m; λ is the starting pressure gradient, m.
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