CN110687153B - Compact sandstone reservoir pore mobility classification and evaluation method - Google Patents
Compact sandstone reservoir pore mobility classification and evaluation method Download PDFInfo
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- 150000003839 salts Chemical class 0.000 claims description 12
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- 238000005516 engineering process Methods 0.000 description 6
- 230000035699 permeability Effects 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
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Abstract
The invention relates to a compact sandstone reservoir pore mobility classification and evaluation method, which comprises the following specific steps: s1, preparing a sample, and performing nuclear magnetic resonance and high-pressure mercury injection test on the sample; s2, according to the mercury inlet saturation S Hg And mercury feed pressure P c Drawing a mercury intrusion curve, a Pittman curve and a fractal curve, determining the boundary of the inter-granular pores and the intra-granular pores according to the boundary of a 'platform segment' and an 'increasing segment' of the mercury intrusion curve, the vertex of the Pittman curve and the turning point of the fractal curve, and dividing the inter-granular pores and the intra-granular pores according to the boundary; s3, according to the relation between a saturated water nuclear magnetic curve and a bound water nuclear magnetic curve, combining the limits of inter-particle pores and intra-particle pores, dividing the inter-particle pores into movable macropores and isolated macropores, and dividing the intra-particle pores into movable micropores and unmovable micropores; and S4, calculating the contents of different types of pores. The method can realize the evaluation of the mobility of different types of pores of the compact sandstone reservoir, so that the mobility evaluation of the pores of the reservoir is more in line with the actual geological condition, and the evaluation result is more accurate.
Description
Technical Field
The invention belongs to the technical field of oil and gas geological exploration, and particularly relates to a method for classifying and evaluating mobility of compact sandstone reservoir pores.
Background
Dense sandstone reservoirs have various pore types such as residual intergranular pores, corrosion pores and clay intergranular pores (see: zhao et al, 2015, gao et al, 2016, lai et al, 2017, 2018), and have large differences in size, distribution and connectivity (see a.sakhaee-pourr and Steven l.bryant,2014; tsukudani et al, 2017). The effect of the complex pore-throat network of tight reservoirs on the reservoir properties, in particular permeability, is particularly pronounced (see Zhao et al, 2015 lai et al, 2016, 2018 schmitt M et al, 2015), the control of which is mainly dependent on the development of mobile pores in the pore system (see Xi et al, 2016. Generally in high permeability sandstones, large enough throat radius tends to connect the pores to each other, with strong fluid mobility (see kaslab et al, 2017), while tight sandstones that develop large amounts of microporosity complicate the porosity-permeability relationship (see Schmitt M et al, 2015 Lai et al, 2016 kaslab et al, 2017; wuhao et al, 2017), with particularly clay-associated microporosities contributing less to fluid flow (see Lai et al, 2016, 2018). Therefore, the development difference of different types of movable pores is an important factor which causes the complex pore connectivity and further influences the macroscopic physical properties of reservoirs (see Huang et al, 2018, xi et al, 2016 Lai et al, 2018; tsukudani et al, 2017), and the fine characterization of the movable pores has important significance for the exploration and development of compact oil and gas.
By utilizing a high-pressure mercury intrusion technique, parameters such as pore throat radius and permeability contribution value can be obtained, and the characterization of the pore throat connectivity size of a compact reservoir through the pore throat radius parameter and the permeability contribution value is a main method for the current pore throat connectivity research (see Xi et al, 2016; wuhao et al, 2017; shotsukudani et al, 2017; qiangqiang et al, 2018; liuhanlin et al, 2018), but the high-pressure mercury intrusion method mainly characterizes the pore throat size distribution and cannot intuitively reflect the flow capacity of fluids in pores with different sizes. Nuclear magnetic resonance technology is one of the important means for obtaining mobile fluid distribution (see Huang et al, 2018; timeConvergence 2016), and the current evaluation of the mobility of the total pore space of a compact reservoir also depends on the nuclear magnetic resonance technology (see Lai et al, 2018). For example, wuhao et al (2015), li min et al (2018), shijian et al (2016), shikaoqian et al (2016), huangang et al (2018), li et al (2018), wuyuping et al (2019) obtain parameters such as mobile fluid saturation, mobile fluid porosity and the like of a compact reservoir by a nuclear magnetic resonance technology, and mobility of the compact reservoir is evaluated by using the parameters to research the mobility and influencing factors of different types of reservoirs, but the mobility of different types of pores is not researched.
From the above, the existing evaluation of the mobility of the pore in the compact sandstone reservoir mostly depends on the parameters of the saturation of the movable fluid, the porosity of the movable fluid and the like obtained by the nuclear magnetic resonance technology, the evaluation of the mobility of the pore is too macroscopic, the representation of the mobility of different types of pores in the compact reservoir is lacked, the understanding of the development law of the movable pore in the compact reservoir is influenced, and the success rate of exploration and development of compact oil and gas is reduced.
Disclosure of Invention
Aiming at the problems that the existing method lacks representation of mobility of different types of pores in a tight reservoir and the like, the invention provides a method for classifying and evaluating the mobility of the pores in the tight sandstone reservoir, which can realize evaluation of the mobility of the different types of pores in the tight sandstone reservoir, so that the mobility evaluation of the pores in the reservoir more conforms to the actual geological condition and the evaluation result is more accurate.
In order to achieve the aim, the invention provides a compact sandstone reservoir pore mobility classification and evaluation method, which comprises the following specific steps:
s1, preparing a sample, and carrying out nuclear magnetic resonance and high-pressure mercury injection test on the sample
Preparing a sample, and sequentially carrying out nuclear magnetic resonance test and high-pressure mercury injection test on the sample to obtain a saturated water nuclear magnetic curve, a bound water nuclear magnetic curve and mercury injection saturation S Hg And mercury feed pressure P c ；
S2, dividing inter-granular pores and intra-granular pores
According to mercury saturation S Hg And mercury feed pressure P c Drawing a mercury intrusion curve, a Pittman curve and a fractal curve, determining the boundary of the inter-granular pores and the intra-granular pores according to the boundary of a 'platform segment' and an 'increasing segment' of the mercury intrusion curve, the vertex of the Pittman curve and the turning point of the fractal curve, and dividing the inter-granular pores and the intra-granular pores according to the boundary;
s3, dividing movable pores and immovable pores
According to the relation between the saturated water nuclear magnetic curve and the bound water nuclear magnetic curve, combining the limits of inter-granular pores and intra-granular pores, dividing the inter-granular pores into movable macropores and isolated macropores, and dividing the intra-granular pores into movable micropores and unmovable micropores;
s4, calculating the contents of different types of pores
Dividing the saturated water nuclear magnetic curve, the bound water nuclear magnetic curve and the abscissa enveloping surface into 4 regions of a movable macropore region, an isolated macropore region, a movable micropore region and an unmovable micropore region, and respectively calculating the area ratio of the four regions to the total enveloping surface to obtain the proportion of the movable macropore, the isolated macropore, the movable micropore and the unmovable micropore to the total pore.
Preferably, in step S1, the specific steps of preparing the sample are: selecting typical sandstone of a compact sandstone reservoir in a research area, preparing a standard core plunger sample with the length of 3cm and the diameter of 2.5cm, and performing salt washing, oil washing and drying treatment to obtain the sample.
Preferably, in step S1, the specific steps of performing the nuclear magnetic resonance test are:
placing the sample into a high-pressure saturated water instrument, vacuumizing, injecting a pre-prepared stratum aqueous solution until the sample is completely saturated, and performing saturated water nuclear magnetism determination to obtain a saturated water nuclear magnetism curve;
and (4) centrifuging the sample to a bound water state and carrying out bound water nuclear magnetic determination to obtain a bound water nuclear magnetic curve.
Preferably, in step S1, before the high-pressure mercury intrusion test is performed, after the nuclear magnetic resonance test is completed, the sample is subjected to salt washing and drying treatment.
Preferably, in step S2, the mercury saturation S is determined according to the mercury injection degree Hg And mercury feed pressure P c The method for drawing the mercury intrusion curve, the Pittman curve and the fractal curve comprises the following steps: at mercury ingress saturation S Hg As abscissa, with mercury feed pressure P c Drawing mercury injection curve for ordinate to obtain mercury saturation S Hg As abscissa, in mercury saturation S Hg With pressure P of mercury feed c Is S of Hg /P c Plotting a Pittman curve for the ordinate to the mercury inlet pressure P c Log of lg (P) c ) As abscissa, in mercury saturation S Hg Log lg (S) of Hg ) Fractal curves were plotted for the ordinate.
Preferably, the vertex of the Pittman curve is S Hg /P c The point at which the maximum is reached is defined as the Swanson parameter, the pore size for which Swanson parameter corresponds is called Rapex, and the Swanson parameter is the point of demarcation between the intergranular and intragranular pores.
Compared with the prior art, the invention has the advantages and positive effects that:
according to the method, on the basis of performing nuclear magnetic resonance testing and high-pressure mercury intrusion testing on a compact sandstone reservoir sample, inter-granular pores and intra-granular pores of the reservoir are divided, movable pores and immovable pores of the inter-granular pores and movable pores and immovable pores of the intra-granular pores are further divided respectively, the proportion of different types of pores is calculated, and classification and evaluation of the mobility of the different types of pores of the compact sandstone reservoir are achieved. The method overcomes the defect that the mobility of the total pores of the compact sandstone reservoir is evaluated only by relying on the nuclear magnetic resonance technology in the prior art, so that the mobility evaluation of the pores of the reservoir is more in line with the actual geological condition, the evaluation result is more accurate, the development rule of the movable pores in the compact sandstone reservoir is more accurately known, and the success rate of the exploration and development of the compact oil gas is effectively improved.
Drawings
FIG. 1 is a flow chart of the method for classifying and evaluating the mobility of tight sandstone reservoir pores according to the present invention;
FIG. 2 is a schematic view of mercury intrusion curves of samples of 7 sections of a new safe edge area according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a Pittman curve of a sample with a length of 7 segments in a new safe edge area according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a fractal curve of a sample with a length of 7 segments in a new safe edge area according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of the pore space corresponding to the "platform section" in the mercury intrusion curve of the new safe edge area with the length of 7 sections according to the embodiment of the present invention;
FIG. 6 is a schematic diagram of the pore corresponding to the "incremental segment" in the mercury intrusion curve of the new safe edge area with 7 segments of length;
FIG. 7 is a schematic diagram illustrating classification of different types of movable pores in a new safe edge area with 7 sections of length according to an embodiment of the present invention;
FIG. 8 is a diagram illustrating the calculation results of different types of pore contents in 7 sections of the new safe edge area according to the embodiment of the present invention.
Detailed Description
The invention is described in detail below by way of exemplary embodiments. It should be understood, however, that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
In the prior art, the evaluation degree of the movable capacity of the compact sandstone reservoir pores depends on the parameters such as the movable fluid saturation, the movable fluid porosity and the like obtained by the nuclear magnetic resonance technology, the evaluation of the movable capacity of the gaps is too macroscopic, the representation of the movable properties of different types of pores in the compact sandstone reservoir is lacked, the understanding of the development law of the movable pores in the compact sandstone reservoir is influenced, and the success rate of the exploration and development of compact oil and gas is reduced.
In order to evaluate the mobility of different types of gaps in the type of compact sandstone reservoir, the invention provides a compact sandstone reservoir pore mobility classification and evaluation method, which considers the types of inter-granular and intra-granular pores of the compact sandstone reservoir, combines high-pressure mercury intrusion with nuclear magnetic resonance analysis, and realizes the division and comparison of the mobility of different types of pores in the compact sandstone reservoir.
Referring to fig. 1, the specific steps are as follows:
s1, preparing a sample, and carrying out nuclear magnetic resonance and high-pressure mercury injection test on the sample
Preparing a sample, and sequentially carrying out nuclear magnetic resonance test and high-pressure mercury pressing test on the sample to obtain a saturated water nuclear magnetic curve, a bound water nuclear magnetic curve and mercury inlet saturation S Hg And mercury inlet pressure P c 。
Specifically, the specific steps for preparing the sample are as follows: selecting typical sandstone of a compact sandstone reservoir in a research area, preparing a standard core plunger sample with the length of 3cm and the diameter of 2.5cm, and performing salt washing, oil washing and drying treatment to obtain the sample. Because salt crystals and crude oil are remained in the original core sample to fill the pores, the standard core plunger sample is subjected to salt washing, oil washing and drying treatment during sample preparation, so that the effect of the nuclear magnetic resonance test and the test measurement of the high-pressure mercury intrusion test are prevented from being influenced by filling the pores in the core sample.
Specifically, the specific steps of performing the nuclear magnetic resonance test are as follows:
placing the sample into a high-pressure saturated water instrument, vacuumizing, injecting a pre-prepared stratum aqueous solution until the sample is completely saturated, and performing saturated water nuclear magnetism determination to obtain a saturated water nuclear magnetism curve;
and (4) centrifuging the sample to a bound water state and carrying out bound water nuclear magnetic determination to obtain a bound water nuclear magnetic curve.
S2, dividing inter-particle pores and intra-particle pores
Drawing a mercury intrusion curve, a Pittman curve and a fractal curve according to the mercury intrusion saturation and the mercury intrusion pressure, determining the boundary of the inter-granular pores and the intra-granular pores according to the boundary of a 'platform segment' and an 'increasing segment' of the mercury intrusion curve, the vertex of the Pittman curve and the turning point of the fractal curve, and dividing the inter-granular pores and the intra-granular pores according to the boundary.
In particular, in mercury ingress saturation S Hg As abscissa, with mercury feed pressure P c Drawing mercury intrusion curve for ordinate to determine mercury intrusion saturation S Hg As abscissa, in mercury saturation S Hg With pressure P of mercury entering c Ratio S of Hg /P c Plotting a Pittman curve for the ordinate to the mercury inlet pressure P c Log of (g) (P) c ) As abscissa, with mercury saturation S Hg Log lg (S) of Hg ) Fractal curves were plotted for the ordinate.
Wherein the vertex of the Pittman curve is S Hg /P c The point at which the maximum is reached is defined as the Swanson parameter, the pore size for which Swanson parameter corresponds is called Rapex, and the Swanson parameter is the point of demarcation between the intergranular and intragranular pores.
S3, dividing movable pores and immovable pores
According to the relation between the saturated water nuclear magnetic curve and the bound water nuclear magnetic curve, the boundary of the inter-granular pores and the intra-granular pores is combined, the inter-granular pores are divided into movable macropores and isolated macropores, and the intra-granular pores are divided into movable micropores and unmovable micropores.
S4, calculating the contents of different types of pores
Dividing the saturated water nuclear magnetic curve, the bound water nuclear magnetic curve and the abscissa enveloping surface into 4 regions of a movable macropore region, an isolated macropore region, a movable micropore region and an unmovable micropore region, and respectively calculating the area ratio of the four regions to the total enveloping surface to obtain the proportion of the movable macropore, the isolated macropore, the movable micropore and the unmovable micropore to the total pore.
Specifically, in step S1, before the high-pressure mercury intrusion test is performed, after the nuclear magnetic resonance test is completed, the sample is subjected to salt washing and drying treatment. In the nuclear magnetic resonance test, the sample saturates the stratum aqueous solution, because the mineralization degree of the stratum aqueous solution is high, the sample has holes which participate in salt crystallization filling, and before the high-pressure mercury pressing test, the salt washing and drying treatment is carried out on the sample, so that the problem that the holes in the sample are filled to block the injection of mercury in the mercury pressing test and influence the mercury pressing test precision is solved.
According to the method, on the basis of nuclear magnetic resonance and high-pressure mercury intrusion test and analysis of the compact sandstone reservoir sample, inter-granular pores and intra-granular pores of the reservoir are divided, movable pores and immovable pores of the inter-granular pores and the intra-granular pores are further divided respectively, the proportion of different types of pores is calculated, and the evaluation of the mobility of different types of pores of the compact sandstone reservoir is realized. The method overcomes the defect that the mobility of the total pore of the compact sandstone reservoir is evaluated only by relying on nuclear magnetic resonance, so that the mobility evaluation of the pore of the reservoir is more consistent with the actual geological condition, the evaluation result is more accurate, and the success rate of exploration and development is effectively improved.
The method of the present invention will be described below by taking classification and evaluation of the pore mobility of 7 tight sandstone reservoir zones of new welfare zone length in the deldos basin as an example.
S1, preparing a sample, and performing nuclear magnetic resonance and high-pressure mercury injection test on the sample.
Selecting typical sandstone of a 7-section compact sandstone reservoir in a new safety margin area of an Eldos basin, preparing a standard core plunger sample with the length of 3cm and the diameter of 2.5cm, washing salt, washing oil and drying to obtain a sample, and sequentially carrying out nuclear magnetic resonance testing and high-pressure mercury intrusion testing by using the same sample. When in nuclear magnetic resonance test, a sample is put into a high-pressure saturated water instrument, a pre-prepared stratum aqueous solution is injected after vacuumizing until the sample is completely saturated, and saturated water nuclear magnetic measurement is carried out to obtain a saturated water nuclear magnetic curve; and centrifuging the sample to a bound water state and carrying out bound water nuclear magnetism determination to obtain a bound water nuclear magnetism curve. Nuclear magnetic resonanceAfter the test is finished, the sample is subjected to salt washing and drying treatment, and high-pressure mercury injection test is carried out to obtain mercury injection saturation S Hg And mercury inlet pressure P c 。
And S2, dividing inter-particle pores and intra-particle pores.
At mercury ingress saturation S Hg As abscissa, with mercury feed pressure P c The mercury intrusion curve is plotted for the ordinate, see fig. 2, where a is the "incremental segment" of the mercury intrusion curve and B is the "plateau segment" of the mercury intrusion curve.
At mercury ingress saturation S Hg As abscissa, in mercury saturation S Hg With pressure P of mercury entering c Is S of Hg /P c Plotting a Pittman curve for the ordinate, see FIG. 3, where there is one vertex, S Hg /P c The point at which the maximum is reached is defined as Swanson parameter, the pore size for Swanson parameter is called Rapex, where C denotes poorly connected intragranular pores, D denotes well connected intergranular pores, and Swanson parameter (or repeat) is the demarcation point between intragranular pores C and intergranular pores D.
At a mercury feed pressure P c Log of lg (P) c ) As abscissa, in mercury saturation S Hg Log lg (S) of Hg ) Fractal curves were plotted for the ordinate. The fractal curve of the 7 sections of compact sandstone reservoirs in the new safe edge region is characterized by two sections, and is shown in fig. 4, wherein the left section corresponds to a large pore throat, the right section reflects a small pore throat, and the turning points of the two sections of fractal curves are basically coincided with the vertex in the Pittman curve.
The above-mentioned demarcation point is identical with the boundary of "increasing section" and "platform section" in mercury-injection curve. After analysis, the "plateau section" is considered to correspond to the large pore and the fine throat, and is an interparticle pore, and is connected by the narrow and small throats or intraparticle pores between the particles to form an approximate "ink bottle type pore" (see fig. 5), and the "incremental section" corresponds to the intraparticle pore, and is an approximate "tree network pore" (see fig. 6).
And determining the boundary of the inter-granular pores and the intra-granular pores according to the boundary of the 'platform segment' and the 'increasing segment' of the mercury intrusion curve, the vertex of the Pittman curve and the turning point of the fractal curve, and dividing the inter-granular pores and the intra-granular pores according to the boundary.
And S3, according to the relation between the saturated water nuclear magnetic curve and the bound water nuclear magnetic curve, combining the boundaries of the inter-particle pores and the intra-particle pores determined in the step S2, dividing the inter-particle pores with good connectivity into movable macropores and isolated macropores, and dividing the intra-particle pores with poor connectivity into movable micropores and immovable micropores. The classification of different types of movable pores of 7 sections of tight sandstone reservoirs in the new safe edge area is shown in figure 7.
And S4, dividing the saturated water nuclear magnetic curve, the bound water nuclear magnetic curve and the abscissa enveloping surface into 4 regions of a movable macropore region, an isolated macropore region, a movable micropore region and an unmovable micropore region, and respectively calculating the area ratio of the four regions to the total enveloping surface to obtain the proportion of the movable macropore, the isolated macropore, the movable micropore and the unmovable micropore to the total pore. Referring to fig. 8, the calculation result shows that the content of inter-granular pores of the 7-section tight sandstone reservoir in the new safe edge area is 34%, and the content of intra-granular pores is 66%. In the interparticle pores, the content of movable macropores accounts for 22.4%, and 11.4% of the interparticle pores lose the movable capacity; the movable micropore content of the intra-granular pores only accounts for 12 percent, and the immovable micropore content of the intra-granular pores reaches 54 percent, which reflects that the intra-granular pores have movability under certain power conditions, but the movability is lower.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are possible within the spirit and scope of the claims.
Claims (4)
1. A compact sandstone reservoir pore mobility classification and evaluation method is characterized by comprising the following specific steps:
s1, preparing a sample, and carrying out nuclear magnetic resonance and high-pressure mercury injection test on the sample
Preparing a sample, and sequentially carrying out nuclear magnetic resonance test and high-pressure mercury injection test on the sample to obtain a saturated water nuclear magnetic curve, a bound water nuclear magnetic curve and mercury injection saturation S Hg And mercury feed pressure P c ；
S2, dividing inter-particle pores and intra-particle pores
According to mercury saturation S Hg And mercury feed pressure P c Drawing a mercury intrusion curve, a Pittman curve and a fractal curve, determining the boundary of inter-granular pores and intra-granular pores according to the boundary of a 'platform section' and an 'increasing section' of the mercury intrusion curve, the vertex of the Pittman curve and the turning point of the fractal curve, and dividing the inter-granular pores and the intra-granular pores according to the boundary; according to mercury saturation S Hg And mercury feed pressure P c The method for drawing the mercury intrusion curve, the Pittman curve and the fractal curve comprises the following steps: at mercury ingress saturation S Hg As abscissa, with mercury feed pressure P c Drawing mercury injection curve for ordinate to obtain mercury saturation S Hg As abscissa, in mercury saturation S Hg With pressure P of mercury entering c Ratio S of Hg /P c Plotting a Pittman curve for the ordinate to the mercury inlet pressure P c Log of lg (P) c ) As abscissa, in mercury saturation S Hg Log lg (S) of Hg ) Drawing a fractal curve for the ordinate; the vertex of the Pittman curve is S Hg /P c Defining the point reaching the maximum value as a Swanson parameter, wherein the pore diameter corresponding to the Swanson parameter is called as Rapex, and the Swanson parameter is a boundary point of the intergranular pores and the intragranular pores;
s3, dividing movable pores and immovable pores
According to the relation between the saturated water nuclear magnetic curve and the bound water nuclear magnetic curve, combining the limits of inter-granular pores and intra-granular pores, dividing the inter-granular pores into movable macropores and isolated macropores, and dividing the intra-granular pores into movable micropores and unmovable micropores;
s4, calculating the contents of different types of pores
Dividing the saturated water nuclear magnetic curve, the bound water nuclear magnetic curve and the abscissa enveloping surface into 4 regions of a movable macropore region, an isolated macropore region, a movable micropore region and an unmovable micropore region, and respectively calculating the area ratio of the four regions to the total enveloping surface to obtain the proportion of the movable macropore, the isolated macropore, the movable micropore and the unmovable micropore in the total pore.
2. The tight sandstone reservoir pore mobility classification and evaluation method of claim 1, wherein in step S1, the concrete steps of preparing the sample are as follows: selecting typical sandstone of a compact sandstone reservoir in a research area, preparing a standard core plunger sample with the length of 3cm and the diameter of 2.5cm, and performing salt washing, oil washing and drying treatment to obtain the sample.
3. The tight sandstone reservoir pore mobility classification and evaluation method of claim 1 or 2, wherein the step S1 of performing the nuclear magnetic resonance test comprises the following specific steps:
putting the sample into a high-pressure saturated water instrument, vacuumizing, injecting a pre-prepared stratum aqueous solution until the sample is completely saturated, and performing saturated water nuclear magnetism measurement to obtain a saturated water nuclear magnetism curve;
and (4) centrifuging the sample to a bound water state and carrying out bound water nuclear magnetic determination to obtain a bound water nuclear magnetic curve.
4. The method for classifying and evaluating the pore mobility of the tight sandstone reservoir of claim 3, wherein in the step S1, before the high-pressure mercury intrusion test is carried out, and after the nuclear magnetic resonance test is finished, the sample is subjected to salt washing and drying treatment.
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