CN107169192B - Method and device for identifying size of karst cave while drilling - Google Patents
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Abstract
The invention provides a method and a device for identifying the size of a karst cave while drilling, wherein a mechanical model of a reservoir containing the karst cave with a preset size is established; according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque; obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The method can accurately predict the size of the karst cave in the reservoir.
Description
Technical Field
The invention relates to the field of oil and gas exploration and development, in particular to a method and a device for identifying the size of a karst cave while drilling.
Background
The reservoir is a place where oil and gas exist and is also a direct target layer for oil and gas exploration and development. For example, in carbonate reservoirs, karst caves are commonly developed, the size of each karst cave ranges from several meters to tens of meters, and serious production accidents and economic losses are often caused because whether the karst cave will be drilled in front or the size of the karst cave encountered by the front drill cannot be identified in the drilling process.
The identification of the size of the karst cave in the reservoir during the drilling process is an international problem, and therefore a method for accurately predicting the size of the karst cave in the reservoir is urgently needed.
Disclosure of Invention
The invention provides a method and a device for identifying the size of a karst cave while drilling, which are used for solving the problem of identifying the size of the karst cave in a reservoir during the drilling process and realizing accurate prediction of the size of the karst cave in the reservoir.
The invention provides a method for identifying the size of a karst cave while drilling, which comprises the following steps:
establishing a mechanical model of a reservoir layer for each size of karst cave according to the sizes of a plurality of preset karst caves;
according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave;
calculating to obtain the relation between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque;
obtaining an actual measurement value between the bit reactive torque of a target karst cave reservoir stratum and the reservoir stratum depth, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and obtaining the size of a karst cave corresponding to the mechanical model.
The invention also provides a device for identifying the size of the karst cave while drilling, which comprises a construction module, a first calculation module, a second calculation module, a third calculation module and an identification module;
the construction module is used for establishing a mechanical model of a reservoir layer for each size of karst cave according to the sizes of a plurality of preset karst caves;
the first calculation module is used for calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir;
the second calculation module is used for calculating the relation between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
the third calculation module is used for determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between the experimentally determined distortion energy density and the bit reaction torque;
the identification module is used for obtaining an actually measured value between the bit reactive torque of the target karst cave reservoir and the reservoir depth, comparing the actually measured value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir and obtaining the size of the karst cave corresponding to the mechanical model.
According to the technical scheme, the mechanical model of the reservoir containing the karst caves with the preset sizes is established; according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque; obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The method can accurately predict the size of the karst cave in the reservoir.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for identifying a size of a karst cave while drilling according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a method for identifying a size of a karst cave while drilling according to a second embodiment of the present invention;
fig. 3 is a schematic structural diagram of a device for identifying a size of a karst cave while drilling according to a third embodiment of the present invention;
fig. 4 is a schematic structural diagram of a device for identifying a size of a karst cave while drilling according to a fourth embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
First, the relationship between the formation stress field, the distortion energy density, and the bit reaction torque of the reservoir according to the present invention will be described.
The rock is influenced by factors such as geothermal heat, autorotation, gravity, and compression, and a force to be restored to its original form is called a ground stress. The reservoir rock is subjected to the ground stress effect, and a ground stress field is formed in a certain area with the reservoir cavern opening as the center. The ground stress field is related to the geological form, for example, the weight of the overlying materials, the depth from the earth surface to the reservoir, different types of rocks are distributed at different depths, the rock density and the thickness are different, and therefore the ground stress fields at different depths are influenced. Meanwhile, the karst caves are different in size and have different ground stress fields at the periphery.
When the rock is acted by external force, the energy is accumulated in the rock, and a certain deformation energy, namely the distortion energy density, is stored. The different ground stress fields around the karst cave have different distortion energy densities corresponding to each point around the karst cave. By determining the influence rule of the reservoir distortion energy density on the bit reaction torque by utilizing a similar principle experiment, the reservoir distortion energy density is high, the reservoir is easy to break, and the bit reaction torque is large; the reservoir distortion energy density is small, the reservoir is not easy to break, and the reaction torque generated by the drill bit is small. Thereby establishing a link between the size of the cavern and its corresponding reactive torque of the drill bit.
Based on the characteristics, the bit reaction torque of each point around the karst cave with different sizes is analyzed in an experiment, the change rule of the bit reaction torque is monitored in the actual drilling process, and the bit reaction torque is compared with the bit reaction torque of each point around the karst cave with different sizes obtained through the experiment analysis, so that the size of the karst cave is accurately identified, and meanwhile, a targeted drilling and development scheme is provided.
Example one
Fig. 1 is a schematic flow chart of a method for identifying a size of a karst cave while drilling according to an embodiment of the present invention, as shown in fig. 1, the method of the embodiment may include:
step 101: establishing a mechanical model of a reservoir layer for each size of karst cave according to the sizes of a plurality of preset karst caves;
the mechanical model of the reservoir may be a geometric model of various shapes, for example, a cubic model containing different sizes of caverns inside. The caverns contained in the cube model are ellipsoidal, the caverns with different sizes have different long axis lengths and short axis lengths, the size of the cavern is determined according to the combination of a plurality of preset long axis lengths and short axis lengths, and then a mechanical model of a reservoir stratum of the cavern is established for each combination of the long axis lengths and the short axis lengths. Meanwhile, the side lengths of the cube models containing different sizes of karst caves are the same.
In the cube model, the x axis and the y axis are horizontal axes, the z axis is a vertical axis, the geometric models and boundary conditions of the karst cave and the surrounding rocks are adopted, the side surfaces of the cube model are extruded by surrounding rocks along the x axis and the y axis, and the bottom surface of the cube is under the action of gravity along the negative direction of the z axis; the top surface of the cube model is stressed by overburden pressure. Thus, the five faces of the cube model except the top face constrain the displacement of the cube model in the three directions x, y, z.
Meanwhile, a finite element method is used for dividing grids on the cube model, the cube model is divided into a plurality of finite interconnected small units, and the physical and mechanical characteristics of each region of the cube model can be accurately acquired by limiting conditions for each small unit, such as limiting the physical and mechanical parameters of each small unit.
Step 102: calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir;
the rock is influenced by factors such as geothermal heat, autorotation, gravity, and compression, and a force to be restored to its original form is called a ground stress. The reservoir rock is subjected to the ground stress effect, and a ground stress field is formed in a certain area with the reservoir cavern opening as the center. The ground stress field is related to the geological form, for example, the weight of the overlying materials, the depth from the earth surface to the reservoir, different types of rocks are distributed at different depths, the rock density and the thickness are different, and therefore the ground stress fields at different depths are influenced. Meanwhile, the karst caves are different in size and have different ground stress fields at the periphery.
The ground stress field of surrounding rocks around the karst cave is changed along with the distance from the karst cave opening, the surrounding rocks within the range of 5 times of the shaft length of the karst cave are selected around the karst cave, the physical and mechanical parameters of each small unit are limited by using a finite element method, and the ground stress field of a reservoir distributed around the karst cave is calculated.
The side surfaces of the cube model act on the ground stress fields along the directions of the x axis and the y axis, and the distribution of the ground stress fields at the periphery of the karst caves is calculated, so that the obvious difference exists between the ground stress fields of reservoirs distributed around the karst caves with different sizes.
Step 103: calculating according to the ground stress field to obtain the relation between the reservoir depth and the reservoir distortion energy density;
when the rock is acted by external force, the energy is accumulated in the rock, and a certain deformation energy, namely the distortion energy density, is stored. Due to the difference of ground stress fields of reservoirs distributed around karst caves with different sizes, the distortion energy density of each point on the periphery of the corresponding karst cave is different. And calculating the corresponding reservoir distortion energy density according to the ground stress field of the reservoir distributed around the karst cave. And acquiring the depth of the reservoir corresponding to the ground stress field of the reservoir distributed around the karst cave, and determining the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the value of the distortion energy density of the reservoir corresponding to the ground stress field of the reservoir.
Step 104: determining a theoretical numerical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque;
bit reactive torque is the force that the bit is subjected to in rotation contact with the rock during drilling of the bit in the reservoir. The reservoir distortion energy density is large, the reservoir is more easily broken, and the reaction torque borne by the drill bit is larger. Conversely, the reservoir distortion energy density is small, and the less the reservoir is broken, the less the reaction torque the drill bit is subjected to. According to the relation between the reservoir distortion energy density and the bit reaction torque and the relation between the reservoir depth and the reservoir distortion energy density, the relation between the reservoir depth and the reservoir distortion energy density can be calculated. And the karst caves with different sizes are in the same reservoir depth, and the corresponding bit reaction torque values are different, so that the theoretical value of the bit reaction torque is obtained.
Step 105: and obtaining an actual measurement value between the bit reactive torque of the target karst cave reservoir stratum and the reservoir stratum depth, comparing the actual measurement value with a theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and obtaining the size of the karst cave corresponding to the mechanical model.
While the reservoir containing the target cavern is actually drilled, a strain monitoring element is mounted on the drill bit. The strain monitoring element converts the torque signal into an electric signal and transmits the electric signal to the ground. And monitoring and recording the actually measured values of the bit reaction torque at different reservoir depths in real time.
And comparing the measured value of the counter torque of the drill bit at a certain reservoir depth with the theoretical value of the counter torque corresponding to the same reservoir depth in the pre-established mechanical model, and determining the measured value of the counter torque is the same as the theoretical value of the counter torque in which mechanical model, so that the size of the target karst cave can be determined.
In the embodiment, a mechanical model of a reservoir containing a karst cave with a preset size is established; according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque; obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The embodiment can accurately predict the size of the karst cave in the reservoir.
Example two
Fig. 2 is a schematic flow chart of a method for identifying a size of a karst cave while drilling according to a second embodiment of the present invention, as shown in fig. 2, the method of this embodiment may include:
step 201: determining physical and mechanical parameters of reservoirs corresponding to the karst caves with different sizes according to the sizes of the plurality of preset karst caves;
the mechanical model of the reservoir may be a geometric model of various shapes, for example, a cubic model containing different sizes of caverns inside. The caverns contained in the cube model are ellipsoidal, the caverns with different sizes have different long axis lengths and short axis lengths, the size of the cavern is determined according to the combination of a plurality of preset long axis lengths and short axis lengths, and then a mechanical model of a reservoir stratum of the cavern is established for each combination of the long axis lengths and the short axis lengths. Meanwhile, the side lengths of the cube models containing different sizes of karst caves are the same.
In the cube model, the x axis and the y axis are horizontal axes, the z axis is a vertical axis, the geometric models and boundary conditions of the karst cave and the surrounding rocks are adopted, the side surfaces of the cube model are extruded by surrounding rocks along the x axis and the y axis, and the bottom surface of the cube is under the action of gravity along the negative direction of the z axis; the top surface of the cube model is stressed by overburden pressure. Thus, the five faces of the cube model except the top face constrain the displacement of the cube model in the three directions x, y, z.
Optionally, physical and mechanical parameters of reservoirs corresponding to the karst caves with different sizes are determined according to the length of the long axis and the length of the short axis of the karst cave. For example, determining the elastic modulus, Poisson's ratio, internal friction angle, cohesion and tensile strength of reservoirs corresponding to the karst caves with different sizes.
Step 202: according to the physical mechanical parameters, establishing a mechanical model of the reservoir corresponding to the karst cave with the size;
the grid is divided on the cube model by using a finite element method, the cube model is divided into a finite plurality of interconnected small units, and each small unit is subjected to a limiting condition, such as limiting the physical and mechanical parameters of each small unit. The physical and mechanical parameters of each small unit comprise: modulus of elasticity, poisson's ratio, internal friction angle, cohesion, tensile strength.
By dividing grids on the cube model by using a finite element method, physical and mechanical parameters of each region of the cube model can be accurately established.
Step 203: according to a mechanical model of a reservoir, taking a karst cave as a center, calculating the vertical ground stress of the reservoir, the horizontal minimum principal stress of the reservoir and the horizontal maximum principal stress of the reservoir which are distributed around the karst cave;
the rock is influenced by factors such as geothermal heat, autorotation, gravity, and compression, and a force to be restored to its original form is called a ground stress. The reservoir rock is subjected to the ground stress effect, and a ground stress field is formed in a certain area with the reservoir cavern opening as the center. The ground stress field is related to the geological form, for example, the weight of the overlying materials, the depth from the earth surface to the reservoir, different types of rocks are distributed at different depths, the rock density and the thickness are different, and therefore the ground stress fields at different depths are influenced. Meanwhile, the karst caves are different in size and have different ground stress fields at the periphery.
The ground stress field of surrounding rocks around the karst cave is changed along with the distance from the karst cave opening, the surrounding rocks within the range of 5 times of the shaft length of the karst cave are selected around the karst cave, the physical and mechanical parameters of each small unit are limited by using a finite element method, and the ground stress field of a reservoir distributed around the karst cave is calculated.
The side surfaces of the cube model act on the ground stress fields along the directions of the x axis and the y axis, and the distribution of the ground stress fields at the periphery of the karst caves is calculated, so that the obvious difference exists between the ground stress fields of reservoirs distributed around the karst caves with different sizes.
Optionally, the crustal stress field of the reservoir distributed around the karst caves with different sizes comprises the vertical crustal stress of the reservoir, the horizontal minimum principal stress of the reservoir and the horizontal maximum principal stress of the reservoir. According to the physical mechanical parameters of the mechanical model of the reservoir, the formula I, the formula II and the formula III, the vertical ground stress of the reservoir, the horizontal minimum main stress of the reservoir and the horizontal maximum main stress of the reservoir can be calculated respectively.
The formula I is as follows:
wherein σvFor reservoir bedVertical ground stress of (a); rhoiIs the formation rock density; representing the passage through a plurality of rock formations, each having a different density, from the surface to the reservoir; g is gravity acceleration, and is 9.8m/s2；hiThe thickness of the rock in the stratum means the thickness of each rock layer which is different from the surface to the reservoir layer through various rock layers.
The formula II is as follows:
wherein σHIs the horizontal maximum principal stress of the reservoir; sigmavIs the vertical geostress of the reservoir; e is the elastic modulus of the reservoir; μ is the poisson's ratio of the reservoir; ppPressure of overburden, α Biot coefficient ∈H、εhTo construct the strain coefficient.
The formula III is as follows:
wherein σhIs the horizontal minimum principal stress of the reservoir; sigmavIs the vertical geostress of the reservoir; e is the elastic modulus of the reservoir; μ is the poisson's ratio of the reservoir; ppPressure of overburden, α Biot coefficient ∈H、εhTo construct the strain coefficient.
Vertical crustal stress of reservoirs distributed around karst caves of different sizes, horizontal minimum main stress of the reservoirs and horizontal maximum main stress of the reservoirs are calculated through a formula I, a formula II and a formula III, crustal stress field cloud charts distributed around the karst caves of different sizes are accurately obtained, and crustal stress field sizes of the reservoirs of all areas are visually obtained. And the different sizes of the caverns are at the same reservoir depth, and the vertical ground stress, the horizontal minimum principal stress and the horizontal maximum principal stress of the corresponding reservoirs are different.
Step 204: acquiring a preset point position on a well track, and determining the depth of the preset point position in a reservoir;
and determining a calculated trajectory of the reservoir distortion energy density according to the borehole trajectory. A wellbore is the trajectory through which a drill bit drills a reservoir from the surface. And selecting a plurality of distortion energy density calculation points as preset point positions in the direction that the well track gradually approaches the karst cave.
Optionally, a plurality of distortion energy density calculation points are selected from a position 10m away from the cave top of the karst cave to a position 2m away from the cave top to serve as preset point positions.
By flexibly designing and selecting the position of the preset point, the distortion energy densities of different reservoir depths can be obtained, so that more borehole tracks are covered when the distortion energy densities are calculated, and the calculation result is more accurate.
Step 205: calculating the distortion energy density at the position of a preset point according to the vertical ground stress of the reservoir, the horizontal minimum principal stress of the reservoir and the horizontal maximum principal stress of the reservoir;
when the rock is acted by external force, the energy is accumulated in the rock, and a certain deformation energy, namely the distortion energy density, is stored. Due to the difference of ground stress fields of reservoirs distributed around karst caves with different sizes, the distortion energy density of each point on the periphery of the corresponding karst cave is different. And calculating the corresponding reservoir distortion energy density according to the ground stress field of the reservoir distributed around the karst cave.
The distortion energy density at the preset point position depends on the vertical ground stress at the preset point position, the horizontal minimum principal stress at the preset point position, the horizontal maximum principal stress at the preset point position and the corresponding physical and mechanical parameters at the preset point position. And calculating the distortion energy density at the position of the preset point according to the formula IV.
The formula four is as follows:
wherein, UdIs the distortion energy density; sigmaHIs the horizontal maximum principal stress of the reservoir; sigmahIs the horizontal minimum principal stress of the reservoir; sigmavIs the vertical geostress of the reservoir; e is the elastic modulus of the reservoir; μ is the poisson's ratio of the reservoir.
Step 206: and combining the reservoir depth corresponding to the preset point position with the distortion energy density to obtain the relation between the reservoir depth and the reservoir distortion energy density.
And determining the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the depth of the preset point position in the reservoir and the reservoir distortion energy density value corresponding to the ground stress field of the reservoir. And the different sizes of the karst caves are in the same reservoir depth, and the corresponding reservoir distortion energy densities are different.
Step 207: determining a theoretical numerical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque;
bit reactive torque is the force that the bit is subjected to in rotation contact with the rock during drilling of the bit in the reservoir. The reservoir distortion energy density is large, the reservoir is more easily broken, and the reaction torque borne by the drill bit is larger. Conversely, the reservoir distortion energy density is small, and the less the reservoir is broken, the less the reaction torque the drill bit is subjected to.
The quantitative relationship of bit reactive torque to reservoir distortion energy density can be determined in a number of ways. For example, the relationship between the reactive torque of the drill bit and the reservoir distortion energy density under different stress field conditions can be experimentally determined by scaling down the mechanical model according to a similar principle.
The experiment determines the quantitative relation between the bit reaction torque and the reservoir distortion energy density, and specifically comprises the following steps:
according to a mechanical model of a reservoir, selecting rock blocks with reduced proportion to establish a rock model, wherein the rock model comprises karst caves with reduced proportion. Selecting a plurality of bit reactive torque calculation points on the periphery of the karst cave with the same scale reduction, drilling the bit reactive torque calculation points on the rock model by using an actual drilling device, and obtaining the bit reactive torque corresponding to different depths in the rock model. Meanwhile, a plurality of reservoir distortion energy density calculation points corresponding to a plurality of drill bit reaction torque calculation points in the rock mass model with the same scale reduction are selected from the mechanical model of the reservoir, the ground stress fields of the plurality of reservoir distortion energy density calculation points are calculated according to physical mechanical parameters corresponding to the plurality of reservoir distortion energy density calculation points, and the reservoir distortion energy densities of the plurality of reservoir distortion energy density calculation points are calculated according to the ground stress fields of the plurality of reservoir distortion energy density calculation points, so that the reservoir distortion energy densities of different reservoir depths are obtained. And finally, fitting according to the reservoir distortion energy densities at different depths in the mechanical model and the bit reaction torque at the corresponding depths in the rock mass model to obtain a quantitative relation between the bit reaction torque and the reservoir distortion energy density.
The quantitative relationship between the bit reaction torque and the distortion energy density is determined through experiments, and is shown as a formula five:
the formula five is as follows: mbt＝kUd+c；
Wherein M isbtIs the bit reaction torque; u shapedIs the reservoir distortion energy density; k. c is an experimental parameter; specifically, the value of k is about 0.7, and the value of c is-1 to 1.
According to the quantitative relation between the reservoir distortion energy density and the bit reaction torque and the relation between the reservoir depth and the reservoir distortion energy density, the relation between the reservoir depth and the reservoir distortion energy density can be calculated. And the drill bit reaction torque values corresponding to the caverns with different sizes are different at the same reservoir depth, so that the theoretical values of the drill bit reaction torques at different reservoir depths are obtained.
The quantitative relation between the bit reaction torque and the reservoir distortion energy density is determined through experiments, so that the relation between the bit reaction torque and the reservoir distortion energy density is more accurate, and the calculated theoretical numerical value of the bit reaction torque corresponding to the reservoir depth is more accurate.
Step 208: and obtaining an actual measurement value between the bit reactive torque of the target karst cave reservoir stratum and the reservoir stratum depth, comparing the actual measurement value with a theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and obtaining the size of the karst cave corresponding to the mechanical model.
While the reservoir containing the target cavern is actually drilled, a strain monitoring element is mounted on the drill bit. The strain monitoring element converts the torque signal into an electric signal and transmits the electric signal to the ground. And monitoring and recording the actually measured values of the bit reaction torque at different reservoir depths in real time.
And comparing the measured value of the counter torque of the drill bit at a certain reservoir depth with the theoretical value of the counter torque corresponding to the same reservoir depth in the pre-established mechanical model, and determining the measured value of the counter torque is the same as the theoretical value of the counter torque in which mechanical model, so that the size of the target karst cave can be determined.
In the embodiment, a mechanical model of a reservoir containing a karst cave with a preset size is established; according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque; obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The embodiment can accurately predict the size of the karst cave in the reservoir.
EXAMPLE III
Fig. 3 is a schematic view of a device for identifying a size of a karst cave while drilling according to a third embodiment of the present invention, as shown in fig. 3, the device of the present embodiment may include: the system comprises a construction module 31, a first calculation module 32, a second calculation module 33, a third calculation module 34 and an identification module 35;
the construction module 31 is configured to establish a mechanical model of a reservoir for each size of cavern according to the sizes of a plurality of preset caverns;
the first calculation module 32 is used for calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir;
the second calculation module 33 is used for calculating the relationship between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
the third calculation module 34 is used for determining a theoretical numerical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque;
the identification module 35 is configured to obtain an actual measurement value between the bit reactive torque of the target karst cave reservoir and the reservoir depth, compare the actual measurement value with a theoretical value, determine a mechanical model corresponding to the target karst cave reservoir, and obtain a size of a karst cave corresponding to the mechanical model.
The specific manner in which the respective modules perform operations has been described in detail in relation to the apparatus in this embodiment, and will not be elaborated upon here.
In the embodiment, a mechanical model of a reservoir containing a karst cave with a preset size is established; calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical numerical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque; and obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with a theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The embodiment can accurately predict the size of the karst cave in the reservoir.
Example four:
fig. 4 is a schematic view of a device for identifying a size of a karst cave while drilling according to a fourth embodiment of the present invention, as shown in fig. 4, the device of the present embodiment may include: a construction module 41, a first calculation module 42, a second calculation module 43, a third calculation module 44, and an identification module 45;
the construction module 41 is configured to establish a mechanical model of a reservoir for each size of cavern according to the sizes of a plurality of preset caverns;
the first calculation module 42 is used for calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir;
the second calculation module 43 is configured to calculate a relationship between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
the third calculation module 44 is used for determining a theoretical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque;
and the identification module 45 is configured to obtain an actual measurement value between the bit reactive torque of the target karst cave reservoir and the reservoir depth, compare the actual measurement value with a theoretical value, determine a mechanical model corresponding to the target karst cave reservoir, and obtain a size of a karst cave corresponding to the mechanical model.
Optionally, the building module 41 specifically includes: a parameter determination unit 411, a processing unit 412;
the parameter determining unit 411 is configured to determine, according to the size of the cavern, a physical-mechanical parameter of the reservoir corresponding to the cavern of the size.
Specifically, the physical and mechanical parameters specifically include: elastic modulus, Poisson's ratio, internal friction angle, cohesion, and tensile strength of the reservoir.
And the processing unit 412 is configured to establish a mechanical model of the reservoir corresponding to the cavern with the size according to the physical mechanical parameters.
The first calculating module 42 specifically includes: a first calculation unit 421, a second calculation unit 422, and a third calculation unit 423;
the first calculation unit 421 is configured to calculate a vertical geostress of the reservoir;
a second calculation unit 422 for calculating a horizontal minimum principal stress of the reservoir;
and a third calculation unit 423 for calculating a horizontal maximum principal stress of the reservoir.
The second calculating module 43 specifically includes: a first determination unit 431, a second determination unit 432, a third determination unit 433;
the first determining unit 431 is configured to obtain a preset point position on the wellbore trajectory, and determine a depth of the preset point position in the reservoir;
a second determining unit 432, configured to calculate a distortion energy density at a preset point position according to the ground stress field;
the third determining unit 433 is configured to combine the reservoir depth and the distortion energy density corresponding to the preset point position to obtain a relationship between the reservoir depth and the reservoir distortion energy density.
The specific manner in which the respective modules perform operations has been described in detail in relation to the apparatus in this embodiment, and will not be elaborated upon here.
In the embodiment, a mechanical model of a reservoir containing a karst cave with a preset size is established; calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir; calculating the relation between the depth of the reservoir and the distortion energy density of the reservoir according to the ground stress field; determining a theoretical numerical value between the bit reaction torque and the reservoir depth according to the relationship between the reservoir depth and the reservoir distortion energy density and the relationship between the experimentally determined distortion energy density and the bit reaction torque; and obtaining an actual measurement value of the bit reaction torque of the target karst cave reservoir stratum, comparing the actual measurement value with a theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and determining the size of the karst cave. The embodiment can accurately predict the size of the karst cave in the reservoir.
Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A method for identifying the size of a karst cave while drilling is characterized by comprising the following steps:
establishing a mechanical model of a reservoir layer for each size of karst cave according to the sizes of a plurality of preset karst caves;
according to the mechanical model of the reservoir, with the karst cave as a center, calculating the ground stress field of the reservoir distributed around the karst cave;
calculating to obtain the relation between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between experimentally determined distortion energy density and the bit reaction torque;
obtaining an actual measurement value between the bit reactive torque of a target karst cave reservoir stratum and the reservoir stratum depth, comparing the actual measurement value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir stratum, and obtaining the size of a karst cave corresponding to the mechanical model;
the relation between the reservoir depth and the reservoir distortion energy density is calculated according to the ground stress field, and comprises the following steps:
acquiring a preset point position on a well track, and determining the depth of the preset point position in the reservoir;
calculating the distortion energy density at the preset point position according to the ground stress field;
and combining the reservoir depth corresponding to the preset point position with the distortion energy density to obtain the relation between the reservoir depth and the reservoir distortion energy density.
2. The method of claim 1, wherein the establishing of the mechanical model of the reservoir for each size of cavern comprises:
determining physical and mechanical parameters of a reservoir corresponding to the karst cave with the size according to the size of the karst cave;
and establishing a mechanical model of the reservoir corresponding to the karst cave with the size according to the physical mechanical parameters.
3. The method of claim 1, wherein the ground stress field comprises:
the vertical geostress of the reservoir, the horizontal minimum principal stress of the reservoir, and the horizontal maximum principal stress of the reservoir.
4. The method according to claim 2, wherein the determining, according to the size of the cavern, the physical-mechanical parameters of the reservoir corresponding to the size of the cavern comprises:
and determining the elastic modulus, Poisson ratio, internal friction angle, cohesion and tensile strength of the reservoir corresponding to the cavern with the size.
5. A karst cave size while drilling identification device is characterized by comprising: the system comprises a construction module, a first calculation module, a second calculation module, a third calculation module and an identification module;
the construction module is used for establishing a mechanical model of a reservoir layer for each size of karst cave according to the sizes of a plurality of preset karst caves;
the first calculation module is used for calculating the ground stress field of the reservoir distributed around the karst cave by taking the karst cave as the center according to the mechanical model of the reservoir;
the second calculation module is used for calculating the relation between the reservoir depth and the reservoir distortion energy density according to the ground stress field;
the third calculation module is used for determining a theoretical value between the bit reaction torque and the reservoir depth according to the relation between the reservoir depth and the reservoir distortion energy density and the relation between the experimentally determined distortion energy density and the bit reaction torque;
the identification module is used for acquiring an actually measured value between the bit reactive torque of a target karst cave reservoir and the reservoir depth, comparing the actually measured value with the theoretical value, determining a mechanical model corresponding to the target karst cave reservoir and obtaining the size of a karst cave corresponding to the mechanical model;
the second calculation module includes: a first determining unit, a second determining unit and a third determining unit;
the first determining unit is used for acquiring a preset point position on a borehole trajectory and determining the depth of the preset point position in the reservoir;
the second determining unit is used for calculating the distortion energy density at the preset point position according to the ground stress field;
and the third determining unit is used for combining the reservoir depth and the distortion energy density corresponding to the preset point position to obtain the relation between the reservoir depth and the reservoir distortion energy density.
6. The apparatus of claim 5, wherein the building module comprises: a parameter determining unit and a processing unit;
the parameter determining unit is used for determining physical and mechanical parameters of a reservoir corresponding to the cavern with the size according to the size of the cavern;
and the processing unit is used for establishing a mechanical model of the reservoir corresponding to the karst cave with the size according to the physical mechanical parameters.
7. The apparatus of claim 5, wherein the first computing module comprises: the device comprises a first calculating unit, a second calculating unit and a third calculating unit;
the first calculation unit is used for calculating the vertical ground stress of the reservoir;
the second calculation unit is used for calculating the horizontal minimum principal stress of the reservoir;
and the third calculation unit is used for calculating the horizontal maximum principal stress of the reservoir.
8. The apparatus according to claim 6, wherein the parameter determining unit is specifically configured to: and determining the elastic modulus, Poisson ratio, internal friction angle, cohesive force and tensile strength of the reservoir corresponding to the cavern with the size according to the size of the cavern.
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