RU2465453C1 - Method of defining pressure in interwell space - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: proposed method comprises measuring gravitational field at well locations and bed pressure at well bottom, revealing dependence between said magnitudes, measuring gravitational field at earth surface in interwell space zone and defining bed pressure in said zone from derived dependencies. In the case of gas deposits, bed pressure at external boundary of reservoir in interwell space zone is defined by special equation. Note here that factors in said equation are defined from dependencies obtained experimentally for well locations between gravitational field variation during deposit development monitoring, bed pressure variation and difference between gravity difference between adjacent sets of measurements. In the case of oil deposits, bed pressure at external boundary of reservoir is defined from another special equation. Note here that factors in this equation are defined from dependencies obtained at well locations on total volume of hydrocarbons extracted from well for time t at total yield q.

EFFECT: higher accuracy and reliability.

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Description

The invention relates to gravimetric exploration, and in particular to methods for determining reservoir pressure in the interwell space for gas and oil wells.

A known method for determining the current gas reserves in a field, its distribution and movement of fluid masses over the field area, including measuring the gravitational field and reservoir pressure, identifying the relationship between these values and its application to determining the current gas reserves, its distribution and movement in the field (see patent RU 2307379, class G01V 7/00, publ. 09/27/2007). However, this method does not allow determining the formation pressure of oil and gas fields in the interwell space.

Currently, during field development, pressure values are measured only at well locations. In the interwell space, approximate pressure values obtained by linear interpolation of data in the wells are used. In this case, zones of local change in pressure values are skipped.

где

причем

определяют как коэффициенты прямых

и

построенных по полученным в точках расположения скважин экспериментальным точкам зависимостей между изменением гравитационного поля g за время мониторинга разработки месторождения, изменением пластового давления ΔР и разностью в значениях изменения силы тяжести между двумя соседними сериями измерений Δg, а для нефтяных месторождений значение пластового давления Р_к контура питания определяют как Р_к=Р₃+ΔР, где

причем α, β и α₁, β₁ определяют как коэффициенты прямых

и Δg=β₁+α₁Q, построенных по полученным в точках расположения скважин экспериментальным точкам зависимости g, ΔР и Δg от суммарного объема Q=qt углеводородов, извлеченных из скважины за время t при объемном дебите q.The objective of the invention is to remedy these disadvantages. The technical result consists in reducing the time of measurement and increasing the accuracy of the data. The problem is solved, and the technical result is achieved by the fact that according to the method for determining the reservoir pressure in the interwell space, including measuring the gravitational field in the field area (at the locations of the wells and in the interwell space) and reservoir pressure P ₃ in the bottom of the wells, identifying the relationship between the changes of these values and determination of the corresponding reservoir pressure in the interwell space from the obtained dependences; for gas fields, the reservoir pressure P _to in the interwell space is defined as

Where

moreover

defined as direct coefficients

and

constructed from the experimental points of the dependencies obtained between the changes in the gravitational field g during the monitoring of field development, the change in reservoir pressure ΔP and the difference in the values of the change in gravity between two adjacent series of measurements Δg, and for oil fields the value of reservoir pressure P _{to the} supply circuit determined as P _to = P ₃ + ΔP, where

moreover, α, β and α ₁ , β _{1 are} defined as the coefficients of the lines

and Δg = β ₁ + α ₁ Q constructed from the experimental points of the dependence of g, ΔР, and Δg on the total volume Q = qt of hydrocarbons extracted from the well during time t at a volumetric flow rate q obtained at the well location points.

Figure 1 shows a map of changes in reservoir pressure within one of the gas fields of the Tyumen region. The map is based on well measurements. In the interwell space, the pressure values are obtained by linear interpolation.

Figure 2 shows a map of pressure changes, constructed according to the wells and the gravitational field - in the inter-well space pressure values are found by variations of gravity, relying on well data, according to the proposed method.

Figure 3 shows the deviation (difference) between the pressure values shown in figures 1 and 2, the error in determining the pressure in the interwell space only from well data. As can be seen from figure 3, the error in determining the pressure can reach significant values - up to 4-5 atmospheres.

Thus, the relationship between the values of g and P is established in the zones of the wells, where they are known, and in the inter-well space, the pressure values are found from the known data of the gravitational field, taking into account the patterns of changes in the space of its relations with pressure.

The presence of relationships between gravity variations and reservoir pressure values at well locations and in inter-well space is currently a proven fact. These dependences correspond to the nature of the processes in the reservoirs associated with the selection of fluids from them. Moreover, the presence of several formulas makes it possible to more accurately find the pressure in the interwell space, since they mutually complement and control each other.

The method for determining the reservoir pressure values in the interwell space from variations in gravity for the case of gas fields consists in applying the empirical formula

- постоянные - коэффициенты этого равенства; ΔР, g - изменения значений пластового давления и гравитационного поля (вариаций силы тяжести) за время мониторинга разработки месторождения t; Δg - разность в значениях вариаций силы тяжести между двумя соседними сериями измерений.Where

- constants are the coefficients of this equality; ΔР, g — changes in reservoir pressure and gravitational field (gravity variations) during the monitoring of field development t; Δg is the difference in the values of the variations of gravity between two adjacent series of measurements.

The constants a, b, c are determined by the coefficients of the lines

от пластового давления ΔР и давления ΔР от разности вариаций силы тяжести Δg между двумя соседними сериями наблюдений на скважинах, по равенствамplotted from the experimental points of the dependencies of the change in values

from reservoir pressure ΔР and pressure ΔР from the difference in variations of gravity Δg between two adjacent series of observations in wells, according to the equalities

Lines (2) and (3) are built at the locations of the wells according to several series of measurements. The coefficients of equation (1) are determined from them, and then at the points of the interwell space by equality (1), changes in reservoir pressure values are found using the values of gravity g variations and its difference Δg known in each of them.

The value of reservoir pressure P _to in the interwell space from the obtained values is determined as

In the case of oil fields, the pressure change in the interwell space is determined by the empirical formula

wherein the dependence coefficients a ₁ , b ₁ , c _{1 are} determined from the expressions

The values of the constants α, β and α ₁ , β _{1 are} determined as the coefficients of the lines

от

и Δg от Q. Здесь Q=qt - объем нефти, извлеченной из скважины за время t при объемном дебите скважины q.constructed at the well locations at the experimental dependency points

from

and Δg from Q. Here Q = qt is the volume of oil extracted from the well during time t at a volumetric flow rate of well q.

The reservoir pressure P _to the supply circuit is defined as P _to = P _s + ΔP. The value of P _s is taken from the data of the well closest to the point of the interwell space. To accurately determine the reservoir pressure, you need to use the data for the two nearest wells located in different directions from this point. In this case, if there is a discrepancy, then it must be eliminated by a known method. The pressure values obtained in this way correspond to their change over time Δt = t ₂ -t ₁ . The pressure at time t ₂ can be determined by the formula P (t ₂ ) = P (t ₁ ) + ΔP.

In the general case, in formulas (1), (4) and (5)

ΔP = P (t _i ) -P (t ₁ ),

g = V _z (t _i ) -V _z (t ₁ ),

Δg = g (t _{i + 1} ) -g (t _i ),

where t ₁ and t _i are the times of the first and i-th series of observations, V _z are the values of the variations of gravity. Pressure P can be equal to any type of reservoir pressure, for example, current or dynamic, pressure on the supply circuit. With a sufficient distance between the points of the interwell space from the existing wells, the funnels of depression do not act on them and the reservoir pressure in them becomes equal to the pressure on the supply circuit P _k (P _s = 0).

Based on the results of the determinations, a map of changes in reservoir pressure values is constructed within the entire field, including the inter-well area.

Thus, the proposed method allows to determine the values of reservoir pressure in the interwell space by variations of gravity obtained when monitoring oil and gas fields on the surface, using the relationship between the values of the gravitational field and pressure at the points of location of the wells. Moreover, all local changes in reservoir pressure values in the interwell space, which are associated with the corresponding changes in the gravitational field, are completely preserved.

Claims (1)

A method for determining reservoir pressure in the interwell space, including measuring the gravitational field at the points of the location of the wells and reservoir pressure _Pz in the bottom of the wells, identifying the relationship between these values, measuring the gravitational field g on the surface of the earth in the interwell space and determining the corresponding reservoir pressure in this region according to the obtained dependences, characterized in that for gas fields the value of reservoir pressure P _k on the supply circuit in the area of interwells n space is defined as

Where

moreover

b ₁ and b _{2 are} defined as the coefficients of the lines

and

constructed from the experimental points of the dependencies obtained between the changes in the gravitational field g during the monitoring of field development, the change in reservoir pressure ΔP and the difference in the values of the change in gravity between two adjacent series of measurements Δg, and for oil fields the value of reservoir pressure P _{to the} supply circuit determined as P _to = P _s + ΔP, where

moreover, α, β and α ₁ , β _{1 are} defined as the coefficients of the lines

and Δg = β ₁ + α ₁ Q constructed from the experimental points of the dependence of g, ΔР, and Δg on the total volume Q = qt of hydrocarbons extracted from the well during time t at a volumetric flow rate q obtained at the well location points.

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