CN115544909B - Equivalent seepage flow method for determining thickness of large-thickness oil reservoir with open top - Google Patents

Abstract

The invention discloses an equivalent seepage resistance method for determining the thickness of a large open-top oil reservoir, which includes: calculating the average daily output of the oil well q _t and the fluid viscosity μ _t according to the production dynamic parameters, oil well and fluid basic parameters. ; Calculate the equivalent seepage resistance height h according to the average daily output of the oil well q _t and the fluid viscosity μ _t ; obtain the thickness h _d of the oil well drilling through the main reservoir development layer based on the drilling data; according to the equivalent seepage resistance height h, the oil well drilling The thickness h _d of the main layer that penetrates the reservoir development is calculated to obtain the thickness H of the large thick reservoir with the top open. Based on the mean seepage resistance method in seepage mechanics, the present invention determines a calculation method suitable for the thickness of large-thick oil reservoirs with open tops. This invention takes into account the influence of production and bottom hole pressure in the actual production conditions of oil wells, which is not only conducive to effective It can accurately judge the size of large-thick oil reservoirs, and also provides a reliable basis for the efficient development of such oil reservoirs.

Description

An equivalent seepage resistance method for determining the thickness of large and thick oil reservoirs with open tops

Technical field

The invention relates to an equivalent seepage resistance method for determining the thickness of a thick oil reservoir with an open top, and belongs to the technical fields of oil and gas field development and reservoir engineering.

Background technique

Our country is in a period of rapid social and economic development. As a major manufacturing country, the development of the real economy cannot be separated from energy. Petroleum energy is of great significance to our country's development. The energy rice bowl must be firmly in our own hands. Among the oil reservoirs that have been put into development in my country, large oil reservoirs account for a certain proportion and are increasingly becoming the main force in oil exploration. Large-thick oil reservoirs include carbonate rocks, volcanic rocks, sandstones with thick sand bodies and other rock mass types. Usually only the top is drilled. They have the characteristics of large thickness, high reserves, and strong heterogeneity. They are very important for increasing my country's oil production. It is of great significance. How to develop this type of oil reservoir reasonably and effectively has become an urgent problem that needs to be solved in the petroleum field. Reservoir thickness refers to the vertical distance from the bottom boundary of the reservoir to the top boundary of the reservoir. Reservoir thickness is an important factor for efficient development of large-thick oil reservoirs, judgment of reservoir size, reservoir research, and production management. crucial parameter.

In the past ten years, many scholars have fully combined the geological characteristics of oil reservoirs and the dynamic characteristics of oil well production, and used statistical analysis methods, material balance methods, numerical simulation methods and other technical methods to study the dynamic changes of the oil-water interface in oil reservoirs, and have obtained some results and understanding, but the calculation of reservoir thickness has not been specifically studied. The existing reservoir thickness calculation methods mainly include statistical methods and wellbore temperature profile estimation methods. The statistical method requires statistics of wells with known reservoir thickness, statistics of the relationship between oil column height of oil and gas reservoirs, geological structural characteristic parameters such as circle source distance and circle source elevation difference, and regression of the empirical calculation of reservoir thickness and these parameters. Mode. Wellbore temperature profile estimation method is a method that uses wellbore temperature profile test data to perform regression to determine reservoir thickness. However, the above methods have obvious shortcomings. The statistical method requires a lot of statistical work, and the empirical calculation formula obtained can only be used for statistical blocks; the wellbore temperature profile calculation method requires on-site wellbore temperature profile testing, and on-site testing This work not only increases the cost of oil field development, but also affects the normal production of oil wells. Therefore, in actual oil reservoirs, only a few typical wells are selected for wellbore temperature profile testing. Furthermore, the reservoir thickness parameters of the vast majority of wells that have not been tested for temperature profile cannot be obtained. value; the numerical simulation method has the following shortcomings: First, this method requires the establishment of a dynamic numerical model of oil well production. On the one hand, the existing numerical simulation model does not consider the influence of gravity, resulting in a certain deviation between the simulation results and the actual calculation results. On the other hand, Due to the large number of model parameters, the simulation results have strong multiple solutions; secondly, the simulated dynamic oil-water interface position is used to calculate the reservoir thickness, which is smaller than the geological thickness of the reservoir. Therefore, for large and thick oil reservoirs with open tops, a dynamic and simpler method for determining reservoir thickness is needed.

Contents of the invention

In order to overcome the problems in the prior art, the present invention provides an equivalent seepage resistance method for determining the thickness of a thick oil reservoir with an open top, which can conveniently, quickly and reliably determine the thickness of a thick reservoir.

The technical solution provided by the present invention to solve the above technical problems is: an equivalent seepage resistance method for determining the thickness of a large and thick oil reservoir with an open top, which includes the following steps:

Step S10: Calculate the average daily output of the oil well q _t and the fluid viscosity μ _t according to the production dynamic parameters, oil well and fluid basic parameters respectively;

Step S20: Calculate the equivalent seepage resistance height h according to the average daily output of the oil well q _t and the fluid viscosity μ _t ;

In the formula: h is the equivalent seepage height, m; P _RA is the bottom boundary pressure of the oil column, Mpa; P _wf is the bottom well flow pressure, Mpa; q _t is the average daily output of the oil well, m ³ /d; μ _t is Fluid viscosity, cP; K is reservoir permeability, mD; r _w is well radius, m; ρ ₀ is crude oil density, g/cm ³ ; B is drainage width, m; L is drainage length, m;

Step S30: Obtain the thickness h _d of the oil well drilling through the main reservoir development layer based on the drilling data;

Step S40: Calculate the thickness H of the thick oil reservoir with the top open based on the equivalent seepage resistance height h and the thickness h _d of the oil well drilling through the main reservoir development layer.

A further technical solution is that the production dynamic parameters include average daily oil production _qo , average daily water production _qw , and average daily gas production _qg .

A further technical solution is that the basic oil well and fluid parameters include reservoir pressure, crude oil volume coefficient, water volume coefficient, gas volume coefficient, crude oil viscosity, bottom hole flow pressure, well radius, permeability, and crude oil density.

A further technical solution is that the calculation formula for the daily average production volume q _t of the oil well is:

q _t ＝q _w B _w +q _o B ₀ +q _g B _g

In the formula: q _t is the average daily production of oil wells, m ³ /d; q _g is the average daily gas production, m ³ /d; q _w is the average daily water production, m ³ /d; q _o is the average daily production Oil volume, m ³ /d; B _w is the volume coefficient of water; B _o is the volume coefficient of crude oil; B _g is the volume coefficient of gas.

A further technical solution is that the calculation formula of the fluid viscosity μ _t is:

μ _t =μ _o (1-f _w )+μ _w f _w

In the formula: μ _t is the fluid viscosity, cP; μ _o is the crude oil viscosity, cP; q _w is the daily average water production, m ³ /d; q _o is the daily average oil production, m ³ /d.

A further technical solution is that the calculation formula in step S40 is:

H＝h+ _hd

In the formula: h is the equivalent seepage height, m; h _d is the thickness of the main layer of oil reservoir development when the well is drilled, m; H is the thickness of the thick oil reservoir with the top open, m.

The present invention has the following beneficial effects: The present invention determines a calculation method suitable for the thickness of a large and thick oil reservoir with an open top based on the average seepage resistance method of seepage mechanics. The present invention takes into account the actual production conditions of the oil well and the bottom of the well. The influence of pressure not only helps to effectively judge the size of thick oil reservoirs, but also provides a reliable basis for the efficient development of such oil reservoirs.

Description of the drawings

Figure 1 is a cuboid fracture-cavity fluid leakage model diagram distributed along a large fault zone in a fault-karst reservoir;

Figure 2 is a schematic diagram of the seepage resistance in zone I and zone II during the seepage process of crude oil in the drainage fluid.

Detailed ways

The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

An equivalent seepage resistance method of the present invention for determining the thickness of a large and thick oil reservoir with an open top includes the following steps:

Step S10, based on the production dynamic parameters (average daily oil production q _o , average daily water production q _w , average daily gas production q _g ), oil well and fluid basic parameters (reservoir pressure, crude oil volume coefficient, water volume coefficient , gas volume coefficient, crude oil viscosity, bottom hole flow pressure, well radius, permeability, crude oil density) to calculate the average daily output of the oil well q _t and fluid viscosity μ _t respectively;

q _t ＝q _w B _w +q _o B ₀ +q _g B _g

In the formula: q _t is the average daily production of oil wells, m ³ /d; q _g is the average daily gas production, m ³ /d; q _w is the average daily water production, m ³ /d; q _o is the average daily production Oil volume, m ³ /d; B _w is the volume coefficient of water; B _o is the volume coefficient of crude oil; B _g is the volume coefficient of gas;

μ _t =μ _o (1-f _w )+μ _w f _w

In the formula: μ _t is the viscosity of the fluid, cP; μ _o is the viscosity of crude oil, cP; q _w is the average daily water production, m ³ /d; q _o is the average daily oil production, m ³ /d;

Step S20: Calculate the equivalent seepage resistance height h according to the average daily output of the oil well q _t and the fluid viscosity μ _t ;

In the formula: h is the equivalent seepage height, m; P _RA is the bottom boundary pressure of the oil column, Mpa; P _wf is the bottom well flow pressure, Mpa; q _t is the average daily output of the oil well, m ³ /d; μ _t is Fluid viscosity, cP; K is reservoir permeability, mD; r _w is well radius, m; ρ ₀ is crude oil density, g/cm ³ ; B is drainage width, m; L is drainage length, m;

Step S30: Obtain the thickness h _d of the oil well drilling through the main reservoir development layer based on the drilling data;

Step S40: Calculate the thickness H of the thick oil reservoir with the top open based on the equivalent seepage resistance height h and the thickness h _d of the oil well drilling through the main reservoir development layer;

H＝h+ _hd

In the formula: h is the equivalent seepage height, m; h _d is the thickness of the main layer of oil reservoir development when the well is drilled, m; H is the thickness of the thick oil reservoir with the top open, m.

In the present invention, based on geological data, a cuboid drainage fluid model of a large thick oil reservoir with an open top is established. The drainage fluid is controlled by the drainage length L = 500m, the drainage width B = 300m and the equivalent seepage height h, as shown in Figure 1 ;

The seepage resistance of crude oil in the leakage fluid of a large thick reservoir with the top open during the seepage process is innovatively defined as zone I seepage resistance and zone II seepage resistance, as shown in Figure 2;

The seepage resistance in zone Ⅰ is the resistance R _Ⅰ of crude oil during the flow process from the bottom boundary of the reservoir to the bottom of the well;

μ _t =μ _o (1-f _w )+μ _w f _w

In the formula: μ _t is the viscosity of the fluid, cP; μ _o is the viscosity of crude oil, cP; f _w is the water content, %; μ _w is the viscosity of the formation water, cP; h is the equivalent seepage height, m; K is the reservoir penetration Rate, mD; B is the drainage width, m; L is the drainage length, m.

The seepage resistance in zone II is the resistance R _II during the radial flow of crude oil to the perforation section of the wellbore;

In the formula: r _w is the radius of the wellbore, m.

Then according to the seepage pressure difference = seepage intensity (output) × seepage resistance, and considering the influence of gravity, the seepage oil flow formula is written:

q _t ＝q _w B _w +q _o B ₀ +q _g B _g

In the formula: PRA is the reservoir pressure, Mpa; P _wf is the bottom well flow pressure, Mpa; q _t oil well output, m ³ /d; q _w is the water production, m ³ /d; q _o is the oil production, m3/d; q _g is the gas production, m ³ /d; B _w is the water volume coefficient; B _o is the crude oil volume coefficient; B _g is the gas volume coefficient.

Substitute the resistance of the two zones into the seepage oil flow equation to obtain the output _qt :

The equivalent seepage height h is obtained by transferring terms and converting units to the seepage oil flow equation:

In the formula: h is the equivalent seepage height, m; P _RA is the bottom boundary pressure of the oil column, Mpa; P _wf is the bottom well flow pressure, Mpa; q _t is the average daily output of the oil well, m ³ /d; μ _t is Fluid viscosity, cP; K is reservoir permeability, mD; r _w is well radius, m; ρ ₀ is crude oil density, g/cm ³ ; B is drainage width, m; L is drainage length, m.

Example

Step 1. Based on the production performance data of Well X1, take the daily average of each production as shown in Table 1, and calculate the average daily output of the oil well;

q _t ＝q _w B _w +q _o B ₀ +q _g B _g

=112.6×2.1251+0.23×1+49884×10 ^-3

＝289.40026m ³ /d

Step 2: Calculate the fluid viscosity;

_μt ＝0.26×(1-0.204)+1.1×0.204＝0.4314cP

Step 3: Substitute the obtained data and basic parameters to calculate the equivalent seepage resistance height;

Step 4: Organize the drilling data and obtain the thickness of the main reservoir development layer drilled by Well X1 = 21m;

Step 5: Add the equivalent seepage resistance height h to the thickness of the oil well drilling through the main reservoir development layer to obtain the thickness of the thick oil reservoir with the top open;

H＝h+ _hd ＝516.8744+21＝537.8324m

From this, it is determined that the reservoir thickness of Well X1 is 537.8324m.

Table 1X1 Well Production Dynamic Table

Table 2X1 well oil well and fluid basic parameters table

The above does not limit the present invention in any form. Although the present invention has been disclosed through the above embodiments, it is not used to limit the present invention. Any skilled person familiar with the art, without departing from the scope of the technical solution of the present invention, The technical content disclosed above can be used to make some changes or modifications to equivalent embodiments with equivalent changes. However, any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention do not deviate from the content of the technical solution of the present invention. and modifications, all still fall within the scope of the technical solution of the present invention.

Claims (4)

1. An equivalent seepage flow method for determining the thickness of a large thick oil reservoir with an open top, comprising the steps of:

step S10, calculating daily average output q of the oil well according to the production dynamic parameters, the oil well and the fluid basic parameters _t Viscosity μ of fluid _t ；

Step S20, according to the daily average output q of the oil well _t Viscosity μ of fluid _t Calculating the equivalent seepage resistance height h;

wherein: h is the equivalent seepage resistance height and the measurement unit m; p (P) _RA Is the bottom boundary pressure of the oil column, and the unit of measurement is Mpa; p (P) _wf Is the bottom hole flow pressure, and measures the unit Mpa; q _t For daily average production of oil well, unit of measurement m ³ /d；μ _t Is the fluid viscosity, the unit of measure cP; k is the permeability of the oil reservoir and the measurement unit mD; r is (r) _w Is the well radius measurement unit m; ρ ₀ Is the density of crude oil, the unit of measurement g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the B is the discharge width and the measurement unit m; l is the leakage length and the measurement unit m;

s30, obtaining the thickness h of the oil well through oil reservoir development main force layer according to the drilling data _d ；

S40, according to the equivalent seepage resistance height h, the thickness h of the oil well drilling through oil reservoir development main force layer _d Calculating to obtain the thickness H of the large-thickness oil reservoir with the open top;

the production dynamic parameters comprise daily average oil yield q _o Daily average water yield q _w Daily average gas yield q _g ；

The oil well and fluid base parameters include reservoir pressure, crude oil volume coefficient, water volume coefficient, gas volume coefficient, crude oil viscosity, bottom hole flow pressure, well radius, permeability, crude oil density.

2. The method of equivalent seepage flow for determining the thickness of an open-topped heavy and oil reservoir of claim 1, wherein said daily average production rate q of said well _t The calculation formula of (2) is as follows:

q _t ＝q _w B _w +q _o B ₀ +q _g B _g

wherein: q _t For daily average production of oil well, unit of measurement m ³ /d；q _g For daily average gas production, m ³ /d；q _w The daily average water yield is measured in m ³ /d；q _o For daily average oil production, unit of measurement m ³ /d；B _w Is the volume coefficient of water; b (B) _o Is the volume coefficient of crude oil; b (B) _g Is the volume coefficient of the gas.

3. An equivalent seepage flow for determining the thickness of an open-topped heavy oil reservoir according to claim 1, wherein the fluid viscosity μ _t The calculation formula of (2) is as follows:

μ _t ＝μ _o (1-f _w )+μ _w f _w

wherein: mu (mu) _t Is the fluid viscosity, the unit of measure cP; mu (mu) _o The viscosity of crude oil is measured in cP; q _w The daily average water yield is measured in m ³ /d；q _o For daily average oil production, unit of measurement m ³ /d；f _w The water content is measured in units; mu (mu) _w Is the formation water viscosity, measured in cP.

4. The method of equal permeability flow resistance for determining the thickness of an open-topped heavy oil reservoir according to claim 1, wherein the calculation formula in step S40 is:

H＝h+h _d

wherein: h is the equivalent seepage resistance height and the measurement unit m; h is a _d The thickness of a main force layer is developed for oil well drilling through an oil reservoir, and the unit of measurement is m; h is the thickness of the large-thickness oil reservoir with the open top, and the unit of measurement is m.