CN113687412B - Method and device for predicting formation pressure between salts, electronic equipment and medium - Google Patents
Method and device for predicting formation pressure between salts, electronic equipment and medium Download PDFInfo
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Abstract
公开了一种盐间地层压力预测方法、装置、电子设备及介质。该方法可以包括：构建盐间地层的岩石物理模型；根据岩石物理模型，计算盐间地层的弹性张量；根据弹性张量，计算每一个深度的正常压实纵波速度；根据每一个深度的正常压实纵波速度，构建正常压实趋势线，计算目标深度的地层压力。本发明通过构建盐间岩石物理模型，获取常压条件的弹性信息，提高了压实趋势线的精度，并结合Eaton地层压力预测方法，能够有效提高地层压力预测精度。
Disclosed are a method, device, electronic equipment and medium for predicting inter-salt formation pressure. The method may include: constructing a petrophysical model of the inter-salt formation; calculating the elastic tensor of the inter-salt formation based on the petrophysical model; calculating the normal compaction longitudinal wave velocity at each depth based on the elastic tensor; Compaction longitudinal wave velocity, construct a normal compaction trend line, and calculate the formation pressure at the target depth. By constructing an inter-salt petrophysical model, the present invention obtains elastic information under normal pressure conditions and improves the accuracy of the compaction trend line. Combined with the Eaton formation pressure prediction method, it can effectively improve the formation pressure prediction accuracy.
Description
Technical Field
The invention relates to the technical field of oil and gas geophysics, in particular to a method, a device, electronic equipment and a medium for predicting formation pressure among salts.
Background
Formation pressure, also known as pore pressure, is an important engineering dessert parameter. In recent years, with the gradual deep research and development of shale oil and gas reservoirs in China, people have deeper understanding on exploitation of domestic sea-phase shale gas resources. In particular, as commercial exploitation of Fuling shale reservoirs proceeds, it has been found that the production of shale reservoirs is generally positively correlated with formation pressure. The accurate formation pressure prediction result can provide important information for determining the mud density in the drilling process, and the proper mud density proportion can reduce pollution of mud to undisturbed formations and reduce the occurrence probability of accidents such as blowout and the like.
The formation pore pressure calculation theory with the highest acceptance today is the undercompact theory proposed by Terzaghi. This theory holds that the formation Pore fluid Pressure (PP: pore Pressure) is equal to the difference between the overburden formation Pressure (OBP: over burdern Pressure) and the vertical effective stress (VES: vertical Effective Stress). OBP may be calculated by density integration of the overburden. Therefore, the core of pore pressure calculation is how to obtain the vertical stress Value (VES) between particles. Accurate VES value determination is the core of the computation PP.
The core of VES calculation requires the construction of a reasonable normal compaction trend (NCT: normal Compaction Trend). During the deposition process of the sand shale stratum, the stratum fluid in the shale pores is gradually discharged due to the deposition compaction effect along with the gradual compaction of the sediment, and accordingly the stratum fluid is displayed as a normal compaction trend line on a logging curve, namely, the density curve gradually increases linearly, the acoustic wave curve gradually decreases, and the resistivity curve gradually increases due to the improvement of mineralization. If the deposit is subjected to additional pressure during compaction causing formation fluid to not be properly expelled, and is in a less compacted state, the log will deviate from the normal trend line accordingly.
Based on the underpressure theory, the current calculation of the formation pore pressure mainly comprises an empirical coefficient method, an equivalent depth method, an Eaton method and a Bowers method.
The empirical coefficient method is applicable to areas where a certain amount of formation pore pressure measured data already exists. And establishing a normal trend line equation of the acoustic time difference by using data such as a midway test, a well completion test oil, an RFT test and the like of the drilled well in the region, and then regressing an empirical coefficient formula to calculate the formation pore pressure. However, the method has the limitation that the formation pressure distribution in the work area must be known quite, and most of the unconventional exploration areas at the present stage have few clinical data and low development level, so the method has strong limitation. Equivalent depth methods are also known as equilibrium depth methods, and are one of the most effective methods in most basins in the world in terms of formation pressure prediction and detection. From the principle of rock mechanics, it is known that the same values of porosity (or other physical parameters reflecting porosity) correspond to the same effective stresses, whether in normal or under-compacted bands. The balanced depth method considers that the porosity value of the observation point in the uncompacted zone is preserved because the formation is fully closed at this point when the depth of burial reaches the equivalent depth in the normal section, and the increased overburden load is applied to the pore fluid afterwards. The Eaton method is a stratum pore pressure calculation method commonly adopted by oilfield companies at home and abroad, and has the characteristics of high calculation accuracy, wide application range and the like. Eaton's method mainly uses the relation of seismic velocity and vertical effective stress, and the method mainly obtains formation pressure based on velocity change trend lines under normal bottom compaction conditions. The powers method is based on determining VES, and taking the unloading state caused by fluid expansion into consideration, and uses OBP to calculate PP, and practice proves that the method is accurate for high-pressure prediction caused by unbalanced compaction.
The conventional formation pressure methods mentioned above are all based on the undercompact theory, and the greatest disadvantage of the undercompact theory is that an NCT curve needs to be constructed artificially, so that in order to avoid the artificial influence brought by the NCT curve, some students try to jump out of the undercompact theory to perform pressure prediction. The fillppone method proposed by fillppone for the gulf of mexico was compared and the method did not require the construction of NCT, by calculating the maximum and minimum compaction rates of the formation, and then the seismic layer velocity converted by the DIX equation, and finally the formation pressure. The method has also developed to some extent later, and is more remarkable in Liu Zhen formula (1993) proposed by Liu Zhen and in cloud thickness formula (1996) proposed by cloud thickness. In recent years, sun (2015) proposes an API method, which performs parameter screening by using a correspondence between formation pressure and other elastic parameters, and constructs a formation pressure prediction model suitable for a specific region.
Most of the existing methods are based on the undercompact theory, but the method has the defect that the prediction result is greatly dependent on the construction of a normal compaction trend line (NCT), and the construction of different NCT curves can directly influence the prediction result. Conventional NCT trend line construction methods are mostly suitable for continuously deposited sea-phase formations, and NCT construction for land-phase salt-to-salt formations needs further investigation. Although some scholars have attempted to jump out of the lack of compaction theory for pressure prediction, most methods have significant regional limitations if the impact of compaction is not considered at all, as compaction is one of the important reasons for aberrant pressure development. Especially for the land-phase salt formations with complex pressure causes, the rock lithology of the land-phase salt formations has extremely severe longitudinal change, the salt rock formations have very good plugging effect on abnormal pressure, and more challenges are faced on how to accurately predict the abnormal pressure of the salt rock formations. Therefore, there is a need for developing a method, apparatus, electronic device, and medium for predicting formation pressure between salts.
The information disclosed in the background section of the invention is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention provides a method, a device, electronic equipment and a medium for predicting formation pressure among salts, which can acquire elastic information under normal pressure conditions by constructing a rock physical model among salts, improve the precision of compaction trend lines, and can effectively improve the prediction precision of formation pressure by combining with an Eaton formation pressure prediction method.
In a first aspect, embodiments of the present disclosure provide a method for predicting formation pressure between salts, comprising:
constructing a rock physical model of the intersalt formation;
according to the petrophysical model, calculating the elastic tensor of the stratum between salts;
calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor;
and constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth.
Preferably, constructing the petrophysical model of the interbed formation comprises: according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture; adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters; calculating wet porosity, and further calculating a wet clay skeleton; according to the DEM theory, adding the wet clay skeleton into the organic-rich salt rock mixture to obtain a wet mineral skeleton; according to the Gassmann theory, dry pores are added to the wet mineral framework to obtain a petrophysical model.
Preferably, the wet porosity is calculated by formula (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>Is the total porosity.
Preferably, the wet clay skeleton is calculated by formula (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is the elastic tensor of clay.
Preferably, the petrophysical model is calculated by equation (3):
wherein,for elastic parameters of pore fluids, refer to Table 1, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of the wet mineral framework.
Preferably, the normal compaction longitudinal wave velocity is calculated by equation (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density for the corresponding depth.
Preferably, the formation pressure at the target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
As a specific implementation of an embodiment of the present disclosure,
in a second aspect, embodiments of the present disclosure further provide an apparatus for predicting formation pressure between salts, including:
the construction module is used for constructing a rock physical model of the stratum between the salts;
the elastic tensor calculation module is used for calculating the elastic tensor of the stratum between the salts according to the rock physical model;
the longitudinal wave speed calculation module is used for calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor;
and the stratum pressure calculation module is used for constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth and calculating stratum pressure of the target depth.
Preferably, constructing the petrophysical model of the interbed formation comprises: according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture; adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters; calculating wet porosity, and further calculating a wet clay skeleton; according to the DEM theory, adding the wet clay skeleton into the organic-rich salt rock mixture to obtain a wet mineral skeleton; according to the Gassmann theory, dry pores are added to the wet mineral framework to obtain a petrophysical model.
Preferably, the wet porosity is calculated by formula (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>Is the total porosity.
Preferably, the wet clay skeleton is calculated by formula (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is of clay typeElastic tensor.
Preferably, the petrophysical model is calculated by equation (3):
wherein,for elastic parameters of pore fluids, refer to Table 1, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of the wet mineral framework.
Preferably, the normal compaction longitudinal wave velocity is calculated by equation (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density for the corresponding depth.
Preferably, the formation pressure at the target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
In a third aspect, embodiments of the present disclosure further provide an electronic device, including:
a memory storing executable instructions;
and a processor executing the executable instructions in the memory to implement the method of inter-salt formation pressure prediction.
In a fourth aspect, the disclosed embodiments also provide a computer readable storage medium storing a computer program which, when executed by a processor, implements the method of inter-salt formation pressure prediction.
The beneficial effects are that:
(1) The construction of compaction trend lines is central to pressure prediction. Because the longitudinal change of the lithology of the stratum between the salts is very severe, the influence of the lithology speed is considered by the pressure prediction method based on the petrophysical modeling, the trend of the speed along with the lithology change can be better described, a more accurate compaction trend line is obtained, and a foundation is laid for the subsequent pressure prediction.
(2) The change in velocity values at different depths in the subsurface may be due to differences in pressure or may be due to dramatic changes in lithology, and is particularly problematic with respect to characteristics of the formation between salts. The method can enable the compaction trend line to eliminate lithology interference, so that pressure prediction is more accurate.
(3) Based on the pressure prediction flow of petrophysical, all input parameters are driven by data based on logging data, so that human factor interference caused by manually determining compaction trend lines by a conventional method is avoided.
(4) The physical model of the rock between the salts constructed for the stratum between the salts can better reflect the elasticity information of the stratum between the salts under the normal pressure condition.
The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the present invention.
Drawings
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.
Fig. 1 shows a schematic diagram of the undercompact theory.
FIG. 2 illustrates a flow chart of inter-salt formation petrophysical modeling according to one embodiment of the present invention.
FIG. 3 shows a flow chart of the steps of a method of predicting formation pressure between salts according to one embodiment of the invention.
FIG. 4 shows a schematic diagram of an exemplary formation of an interbalided formation in accordance with an embodiment of the present invention.
Fig. 5 a-5 d show schematic diagrams of well logs according to an embodiment of the invention.
FIG. 6 illustrates a schematic diagram of normal compaction trend lines for longitudinal wave velocities according to an embodiment of the present invention.
FIG. 7 shows a schematic diagram of a pressure prediction result according to an embodiment of the present invention.
FIG. 8 illustrates a block diagram of an apparatus for predicting formation pressure between salts in accordance with one embodiment of the invention.
Reference numerals illustrate:
201. constructing a module; 202. an elastic tensor calculation module; 203. a longitudinal wave speed calculation module; 204. and the formation pressure calculation module.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention are described below, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein.
Fig. 1 shows a schematic diagram of the undercompact theory. The theory holds that the overburden formation pressure is equal to the sum of the formation pore fluid pressure and the vertical effective stress. The physical meaning may be expressed as the pressure value of the fluid in the pore space is equal to the sum of the overburden formation pressures minus the vertical stress between the framework particles. OBP is relatively well calculated, and by using a density log, it can be calculated by integrating the density of the overburden. Therefore, the core of pore pressure calculation is how to obtain the vertical stress Value (VES) between particles. Accurate VES value determination is the core of the computation PP. VES may be calculated using the difference between the formation velocity at normal pressure and the velocity at the abnormal pressure. The formation velocity under abnormal pressure, namely the velocity obtained by underground actual measurement, can be obtained by acoustic time difference logging, and the formation velocity under normal pressure needs to be obtained based on NCT curve. In summary, the key to formation pressure calculation is how to obtain the VES values, while the key to VES value calculation is the determination of the NCT curves.
FIG. 2 illustrates a flow chart of inter-salt formation petrophysical modeling according to one embodiment of the present invention.
The invention provides a method for predicting formation pressure among salts, which comprises the following steps:
constructing a rock physical model of the intersalt formation; in one example, constructing a petrophysical model of an interbed formation includes: according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture; adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters; adding wet pores into clay to obtain wet clay; according to the DEM theory, adding wet clay into the organic salt rock mixture to obtain a wet mineral framework; according to the Gassmann theory, dry pores are added to the wet mineral framework to obtain a petrophysical model, as shown in FIG. 2.
The VRH average theoretical formula is:
wherein i represents an i-th mineral, f i As the volume content percentage of the minerals, the volume percentage of each mineral changes with the depth, M VRH As an intersalt mixture, M i The elastic modulus of the ith mineral, including bulk modulus and shear modulus, is shown in Table 1, for different regionsThe modulus of elasticity of minerals may be slightly different, particularly based on local laboratory test samples.
TABLE 1
The DEM theory is formula (9), kerogen is added into the mixture between the salts through formula (9), and finally the elastic tensor of the mixture rich in organic rock salt is obtained:
wherein K is 1 ，μ 1 For bulk modulus and shear modulus of the mixture between salts, K 2 ，μ 2 Bulk modulus and shear modulus, K, of kerogen mix1 ，μ mix1 For the bulk modulus and shear modulus of the intersalt mixture, y is the volume percent of kerogen, P and Q are the form factors that control the shape of the inclusion as a function of depth.
The wet porosity is calculated by formula (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>The total porosity can be obtained directly from the log.
Then the wet clay skeleton is calculated by equation (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is the elastic tensor of clay.
And adding the wet clay skeleton into the organic rock salt mixture by using a DEM theory to obtain the wet mineral skeleton.
Dry porosity is calculated by equation (10):
adding the dry pore space into the wet mineral framework by using a formula (3) to obtain a petrophysical model:
wherein,for elastic parameters of pore fluids, refer to Table 1, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of the wet mineral framework.
The mineral composition, porosity and density log for each depth are input to a petrophysical model, and the elastic tensor of the formation between the salts at that depth is calculated.
Calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor of the stratum between the salts; in one example, the normal compaction longitudinal wave speed is calculated by equation (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density for the corresponding depth.
Constructing a normal compaction trend line about the longitudinal wave velocity according to the normal compaction longitudinal wave velocity of each depth, and calculating the formation pressure of the target depth; in one example, formation pressure at a target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
The normal compaction trend line (NCT) of the prior art, typically a velocity profile that increases slowly with depth, is calculated by substituting the velocity on the trend line into equation (5) to obtain the pressure value of the conventional method. However, the method ignores the influence of lithology change on NCT trend, the method brings the influence of lithology change of different depths into pressure prediction, so that the newly constructed normal compaction trend line is not an approximate straight line, but is a curve which continuously changes along with the depth, and the speed on the trend line of the method is brought into a formula (5), thus the stratum pressure value of the target depth can be calculated.
The invention also provides a device for predicting the formation pressure among salts, which comprises:
the construction module is used for constructing a rock physical model of the stratum between the salts; in one example, constructing a petrophysical model of an interbed formation includes: according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture; adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters; adding wet pores into clay to obtain wet clay; according to the DEM theory, adding wet clay into the organic salt rock mixture to obtain a wet mineral framework; according to Gassmann theory, dry pores are added to wet mineral frameworks to obtain a petrophysical model.
The VRH average theoretical formula is:
wherein i represents an i-th mineral, f i As the volume content percentage of the minerals, the volume percentage of each mineral changes with the depth, M VRH As an intersalt mixture, M i For the i-th mineral, the elastic modulus, including the bulk modulus and the shear modulus, the specific values are shown in table 1, and the elastic modulus of the minerals in different regions may be slightly different, specifically based on the local laboratory test samples.
The DEM theory is formula (9), kerogen is added into the mixture between the salts through formula (9), and finally the elastic tensor of the mixture rich in organic rock salt is obtained:
wherein K is 1 ，μ 1 For bulk modulus and shear modulus of the mixture between salts, K 2 ，μ 2 Bulk modulus and shear modulus, K, of kerogen mix1 ，μ mix1 For the bulk modulus and shear modulus of the intersalt mixture, y is the volume percent of kerogen, P and Q are the form factors that control the shape of the inclusion as a function of depth.
The wet porosity is calculated by formula (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>The total porosity can be obtained directly from the log.
Then the wet clay skeleton is calculated by equation (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is the elastic tensor of clay.
And adding the wet clay skeleton into the organic rock salt mixture by using a DEM theory to obtain the wet mineral skeleton.
Dry porosity is calculated by equation (10):
adding the dry pore space into the wet mineral framework by using a formula (3) to obtain a petrophysical model:
wherein,for elastic parameters of pore fluids, refer to Table 1, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of the wet mineral framework.
And the elastic tensor calculation module is used for inputting the mineral composition, the porosity and the density logging curve of each depth into the petrophysical model and calculating the elastic tensor of the stratum among the depth salts.
The longitudinal wave speed calculation module calculates the normal compaction longitudinal wave speed of each depth according to the elastic tensor of the stratum between the salts; in one example, the normal compaction longitudinal wave speed is calculated by equation (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density for the corresponding depth.
The stratum pressure calculation module is used for constructing a normal compaction trend line related to the longitudinal wave speed according to the normal compaction longitudinal wave speed of each depth and calculating stratum pressure of the target depth; in one example, formation pressure at a target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
The present invention also provides an electronic device including: a memory storing executable instructions; and the processor runs the executable instructions in the memory to realize the method for predicting the formation pressure among the salts.
The present invention also provides a computer readable storage medium storing a computer program which when executed by a processor implements the method of inter-salt formation pressure prediction described above.
In order to facilitate understanding of the solution and the effects of the embodiments of the present invention, four specific application examples are given below. It will be understood by those of ordinary skill in the art that the examples are for ease of understanding only and that any particular details thereof are not intended to limit the present invention in any way.
Example 1
FIG. 3 shows a flow chart of the steps of a method of predicting formation pressure between salts according to one embodiment of the invention.
As shown in fig. 3, the method for predicting the formation pressure between salts includes: step 101, constructing a rock physical model of an intersalt stratum; 102, calculating the elastic tensor of the stratum between salts according to the rock physical model; step 103, calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor; and 104, constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth.
FIG. 4 shows a schematic diagram of a typical formation of an interbed formation according to one embodiment of the present invention, consisting of two sets of rock salts, one set of interbed formation, with a rock salt thickness typically around 10-25 meters, with low porosity, low permeability differential, which may provide a better pressure containment. The thickness of the stratum between the salts is usually between 5 and 38 meters, and the porosity of the stratum between the salts is relatively high due to the thermal evolution of organic matters and the like, so that the stratum between the salts is an unconventional reservoir which is self-produced and self-stored.
Fig. 5 a-5 d show schematic diagrams of well logs according to an embodiment of the invention. Gamma, longitudinal wave velocity, density and porosity are sequentially from left to right. Logging of the rock formations correspondingly exhibits low GR, high velocity, low density, low porosity, while the inter-salt formations exhibit high GR, low velocity, medium density, high porosity.
FIG. 6 illustrates a schematic diagram of normal compaction trend lines for longitudinal wave velocities according to an embodiment of the present invention. As can be seen from the figure, the dashed line is the NCT line constructed by the conventional method, the gray solid line is the NCT line calculated by the present method, and the black solid line is the measured longitudinal wave velocity. The three curves are quite obvious in characteristics, the dotted line reflects the trend of the speed along with the depth change, and the three curves are approximately in a straight line; the gray solid line and the actually measured black solid line show a severe variation trend, and the depth section is a salt prosody layer with severe lithology variation as compared with the geological stratification result. Thus, the periodic jitter of the measured curve is largely caused by the drastic changes in lithology longitudinal direction. The velocity is a parameter that is commonly affected by pore pressure and lithology, and it is apparent that using a single NCT line cannot describe a salt prosody layer with severe lithology changes, which only considers the effect of pore pressure on velocity, but ignores the effect of lithology. And finally, the pore pressure prediction result contains lithology information, so that the final pressure prediction result is suddenly high and suddenly low. However, the gray NCT line constructed by the inter-salt petrophysical model of the method changes along with the change of lithology, and the result contains the change information of the longitudinal lithology, so that the prediction result of the pore pressure is more accurate.
FIG. 7 shows a schematic diagram of a pressure prediction result according to an embodiment of the present invention. The open dots are mud density, the gray curve is the conventional pore pressure prediction result, and the black thick solid line is the prediction result of the new method. In contrast, the conventional predictions shown in gray exhibit periodic jitter due to the severe longitudinal variation of the lithology between salts, and the pore pressure predictions exceed the mud density over many depth segments. The mud density profile reflects the upper limit of formation pressure. When the pore pressure is greater than the mud density, accidents such as kick and even blowout occur, so that in pressure prediction, the rationality of a prediction result is generally measured by using the pore pressure. The influence of lithology on pressure result prediction is eliminated based on the prediction result of the method, most of the pressure prediction value is lower than the mud density value, and compared with the conventional method, the prediction result is more accurate and reasonable.
Example 2
FIG. 8 illustrates a block diagram of an apparatus for predicting formation pressure between salts in accordance with one embodiment of the invention.
As shown in fig. 8, the apparatus for predicting the formation pressure between salts includes:
a construction module 201 for constructing a petrophysical model of the formation between salts;
the elastic tensor calculation module 202 calculates the elastic tensor of the formation between the salts according to the petrophysical model;
the longitudinal wave speed calculation module 203 calculates the normal compaction longitudinal wave speed of each depth according to the elastic tensor;
the formation pressure calculation module 204 constructs a normal compaction trend line from the normal compaction longitudinal wave velocity for each depth and calculates formation pressure for the target depth.
Alternatively, constructing the petrophysical model of the interbed formation includes: according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture; adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters; calculating wet porosity, and further calculating a wet clay skeleton; according to the DEM theory, adding the wet clay skeleton into the organic salt rock mixture to obtain a wet mineral skeleton; according to Gassmann theory, dry pores are added to wet mineral frameworks to obtain a petrophysical model.
Alternatively, the wet porosity is calculated by formula (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>Is the total porosity.
Alternatively, the wet clay skeleton is calculated by formula (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is the elastic tensor of clay.
Alternatively, the petrophysical model is calculated by equation (3):
wherein,for elastic parameters of pore fluids, refer to Table 1, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of the wet mineral framework.
Alternatively, the normal compaction longitudinal wave velocity is calculated by equation (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density for the corresponding depth.
Alternatively, the formation pressure at the target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
Example 3
The present disclosure provides an electronic device including: a memory storing executable instructions; and the processor runs the executable instructions in the memory to realize the method for predicting the formation pressure among the salts.
An electronic device according to an embodiment of the present disclosure includes a memory and a processor.
The memory is for storing non-transitory computer readable instructions. In particular, the memory may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, random Access Memory (RAM) and/or cache memory (cache), and the like. The non-volatile memory may include, for example, read Only Memory (ROM), hard disk, flash memory, and the like.
The processor may be a Central Processing Unit (CPU) or other form of processing unit having data processing and/or instruction execution capabilities, and may control other components in the electronic device to perform the desired functions. In one embodiment of the present disclosure, the processor is configured to execute the computer readable instructions stored in the memory.
It should be understood by those skilled in the art that, in order to solve the technical problem of how to obtain a good user experience effect, the present embodiment may also include well-known structures such as a communication bus, an interface, and the like, and these well-known structures are also included in the protection scope of the present disclosure.
The detailed description of the present embodiment may refer to the corresponding description in the foregoing embodiments, and will not be repeated herein.
Example 4
Embodiments of the present disclosure provide a computer readable storage medium storing a computer program which when executed by a processor implements the method of inter-salt formation pressure prediction.
A computer-readable storage medium according to an embodiment of the present disclosure has stored thereon non-transitory computer-readable instructions. When executed by a processor, perform all or part of the steps of the methods of embodiments of the present disclosure described above.
The computer-readable storage medium described above includes, but is not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or removable hard disk), media with built-in rewritable non-volatile memory (e.g., memory card), and media with built-in ROM (e.g., ROM cartridge).
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention has been given for the purpose of illustrating the benefits of embodiments of the invention only and is not intended to limit embodiments of the invention to any examples given.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.
Claims (8)
1. A method of predicting formation pressure between salts, comprising:
constructing a rock physical model of the intersalt formation;
according to the petrophysical model, calculating the elastic tensor of the stratum between salts;
calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor;
constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth;
calculating the normal compaction longitudinal wave velocity by the formula (4):
wherein v is p_depth For normally compacting longitudinal wave velocityThe degree, K and mu are elastic tensors, and ρ is the total density of the corresponding depth;
wherein the formation pressure at the target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
2. The method of inter-salt formation pressure prediction of claim 1, wherein constructing a petrophysical model of the inter-salt formation comprises:
according to VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain an inter-salt mixture;
adding kerogen into the intersalt mixture according to the DEM theory to obtain an intersalt mixture rich in organic matters;
calculating wet porosity, and further calculating the elastic tensor of the wet clay skeleton;
according to the DEM theory, adding the wet clay skeleton into the mixture between the organic-rich salts to obtain a wet mineral skeleton;
according to the Gassmann theory, dry pores are added to the wet mineral framework to obtain a petrophysical model.
3. The method of predicting the formation pressure between salts of claim 2, wherein the wet porosity is calculated by equation (1):
wherein,is the wet porosity of clay, f c In order to consider the volume percentage of clay in the pores, < >>f c m In order to make up the volume percentage of clay in the mineral irrespective of the pores, < >>Is the total porosity.
4. A method of predicting formation pressure between salts as claimed in claim 3, wherein the elastic tensor of the wet clay skeleton is calculated by equation (2):
wherein M is wet Is the elastic tensor of wet clay skeleton, M clay Is the elastic tensor of clay.
5. The method of predicting formation pressure between salts of claim 2, wherein the petrophysical model is calculated by equation (3):
wherein,as elastic parameter of pore fluid, M mix2 Is the elastic tensor of the petrophysical model, M mix1 Is the elastic tensor of wet mineral framework +.>Is dry porosity.
6. An inter-salt formation pressure prediction apparatus, comprising:
the construction module is used for constructing a rock physical model of the stratum between the salts;
the elastic tensor calculation module is used for calculating the elastic tensor of the stratum between the salts according to the rock physical model;
the longitudinal wave speed calculation module is used for calculating the normal compaction longitudinal wave speed of each depth according to the elastic tensor;
the stratum pressure calculation module is used for constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth and calculating stratum pressure of the target depth;
calculating the normal compaction longitudinal wave velocity by the formula (4):
wherein v is p_depth For normal compaction longitudinal wave velocity, K and μ are elastic tensors, ρ is the total density of the corresponding depth;
wherein the formation pressure at the target depth is calculated by equation (5):
wherein P is p To-be-calculated pressure value for target depth, P ov To overburden pressure value, P w And v is the measured speed value of the target depth for the hydrostatic pressure of the depth to be solved.
7. An electronic device, the electronic device comprising:
a memory storing executable instructions;
a processor executing the executable instructions in the memory to implement the method of inter-salt formation pressure prediction of any one of claims 1-5.
8. A computer readable storage medium, characterized in that the computer readable storage medium stores a computer program which, when executed by a processor, implements the method of predicting the formation pressure between salts of any one of claims 1-5.
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