CN102562052B - Method for recognizing harm bodies of casing failure of shallow layer of close well spacing - Google Patents

Abstract

A kind of method for recognizing harm bodies of casing failure of shallow layer of close well spacing.The method comprises the following steps: (1) determines that shallow-layer cover damages high nip pressures source, determines there is harm body thus; (2) calmodulin binding domain CaM Geologic Structure Feature, sand-body distribution situation, determine whether there is Reservoir Body, determines to there is harm body thus; (3) shallow drilling harm body forms Analysis on Mechanism; (4) geostatic stress prediction and calculating; (5) rock mechanics parameters test; (6) shallow drilling harm body identification and prediction of formation pressure engineer applied.The method Accurate Prediction goes out to endanger body scope, the degree of depth and shallow-layer pressure coefficient, for shallow-layer Tao Sun district's drilling well provides accurate, full and accurate geologic data, on this basis, formulates this block safety drilling scheme, for original oil zone drilling well safely and fast provides strong guarantee.

Description

Method for recognizing harm bodies of casing failure of shallow layer of close well spacing

Technical field:

The present invention relates to drilling engineering technical field, particularly a kind of method for recognizing harm bodies of casing failure of shallow layer of close well spacing.

Background technology:

Each oil field, the world all there occurs casing failure to some extent, comprises North America, Russia, the North Sea, South America, Southeast Asia, and China.By the end of the end of the year 2009, Daqing oil field will find casing damaged well about 12000 mouthfuls altogether, and its middle-shallow layer casing damaged well accounts for about 30%.In long-term exploitation, the injecting process, under every active force, easily there is shallow-layer cover damage in sleeve pipe.After cover damages, due to long-term toward the water filling of shallow-layer well section, understratum high-pressure oil gas by shallow-layer cover damage point leak outside and the non-sealing of casing annulus or sealing of poor quality, deep formation oil-gas migration forms the reasons such as Secondary Gas Pools to shallow-layer, and shallow-layer pressure also increases gradually, forms shallow-layer harm body.Shallow-layer harm body refers to the abnormal pressure sand body or immersion mud shale body that are formed gradually during oil field development at tender more than two sections non-exploitation reservoirs.Because shallow-layer cover damages the harm generation area of body, growth scope and harm form, there is uncertainty, therefore damage in the wellbore construction process of higher-pressure region at shallow-layer cover and easily occur the complex accident such as water logging, well slough, bit freezing, blowout, abandoned footage.

Summary of the invention:

In order to solve Problems existing in background technology, the invention provides a kind of method for recognizing harm bodies of casing failure of shallow layer of close well spacing, the method Accurate Prediction goes out to endanger body scope, the degree of depth and shallow-layer pressure coefficient, for shallow-layer Tao Sun district's drilling well provides accurate, full and accurate geologic data, on this basis, this block safety drilling scheme is formulated.For original oil zone drilling well safely and fast provides strong guarantee.

The technical solution used in the present invention is: this method for recognizing harm bodies of casing failure of shallow layer of close well spacing comprises the following steps:

Method for recognizing harm bodies of casing failure of shallow layer of close well spacing forms Analysis on Mechanism by shallow drilling harm body, geostatic stress prediction is tested with calculating and rock mechanics parameters, according to target area Geologic Structure Feature, sand-body distribution situation, well logging and log data, set up survey region geological model, and determine corresponding fringe conditions, use method for numerical simulation, predict geopressure abnormal conditions and reservoir stress distribution situation, identification object region drilling well harm body, and determine harm body influence basin, formulate drilling well countermeasure on this basis:

(1) determine that shallow-layer cover damages high nip pressures source, determine there is harm body thus:

After A, shallow-layer cover damages, water injection well is long-term toward the water filling of shallow-layer well section;

B, bottom oil layer high-pressure oil gas, by annular space in sleeve pipe, leak outside at shallow-layer cover damage point and enter upper formation;

C, understratum high-pressure oil gas are migrated to top by the sleeve pipe external space;

(2) calmodulin binding domain CaM Geologic Structure Feature, sand-body distribution situation, determine whether there is Reservoir Body, determines to there is harm body thus;

(3) shallow drilling harm body forms Analysis on Mechanism:

By coring in the past, the data such as density log carried out testing and testing.

A, mud shale layer shallow drilling harm body

Submerging test perpendicular to stratum bedding: the change utilizing X-Ray to detect water saturation in rock core is the technology of current comparative maturity, the position of water can be judged according to the X-Ray value before and after rock sample immersion, again by the time of measuring, just can calculate the immersion speed of mud stone, from result of the test: the immersion parameter of mud stone: mud stone immersion intensity, immersed depth and immersion speed, the impact of the main difference by cap rock pore pressure.

Along the interface submerging test of mud shale bedding: edge is perpendicular to direction, mud stone bedding interface and the submerging test along direction, mud stone bedding interface, the immersion speed describing mud stone slows down with the increase of soaking time, until immersion speed is zero, immersion speed and immersed depth are the function of difference between reservoir pre ssure and injection pressure, pressure reduction is larger, immersion speed and immersed depth also larger;

Mud stone water content is on the impact of its mechanical characteristic: the size of its cohesive strength of dissimilar mud shale and angle of internal friction has very big difference, but after immersion, its cohesive strength and angle of internal friction have and reduce significantly, and slope of a curve size description rock sample is to the sensitivity of immersion;

Mud shale drilling well harm body formation mechenism: injection pressure exceedes the fracture pressure of mud shale layer, and water enchroachment (invasion) scope is fracture length and length of flooding sum;

Crack initiation model: Terzaghi pattern, Shi Difen pattern, yellow flourish cup pattern;

Horizontal joint crack initiation pattern: when water injection pressure exceedes horizontal joint initial cracking pressure, the first crack initiation of mud shale layer, forms horizontal fracture, and Reservoir Fluid, form shallow drilling harm body;

B, independent sand body shallow drilling harm body

Geostatic stress derive from remaining palaeo-tectonic stress, stratum on cover water pressure gradient etc. in gravity, the motion collision of continental plate, stratum.Therefore geostatic stress is the internal stress of objective reality in subterranean body.In the rock mass of underground, there are three orthogonal main geostatic stress on direction, namely to be conducted oneself with dignity the main geostatic stress σ H of vertical geostatic stress σ v and two horizontal direction caused and σ h by rock mass.Generally, three main stress bares are unequal.

Geostatic stress computation model:

Vertical geostatic stress computation model:

Switzerland geologist Heim thinks that vertical geostatic stress σ v is caused by superstratum gravity, and it changes along with density of earth formations and the degree of depth, and therefore density available well-log information obtains vertical geostatic stress:

${\mathrm{\σ}}_v={\∫}_0^H\mathrm{\ρ}\left(h\right)\·g\·dh---(3-1)$

In formula: h is stratum buried depth; The function that ρ (h) changes with depth of stratum h for density of earth formations; G is acceleration of gravity.

Flatly stress calculation model: Jin Nike pattern, Mattews and Kelly model, Terzaghi model, Anderson model, Neberry model, two are to the ground stress model such as not

Suppose that stratum extrudes the original place minimum principal stress drawn to one direction, unidirectionally extruded result is exactly that stratum is in one direction by tectonic stress effect, and another direction there is no tectonic stress, but in fact majority of case is really not so, tectonic stress exists in all directions all substantially, and be unequal, the flourish cup professor of the Huang of University of Petroleum has drawn the relational expression of following expression geostatic stress size on Research foundation for many years:

${\mathrm{\σ}}_H=(\frac{{\mathrm{\μ}}_s}{1-{\mathrm{\μ}}_s}+\mathrm{\β})({\mathrm{\σ}}_v-{\mathrm{\αP}}_p)$

Geostatic stress result of calculation: use density log data and degree of depth data, each degree of depth geostatic stress value can be obtained.

Rock mechanics parameters is tested:

Test for tensile strength: measure tensile strength of rock.

Single shaft and triaxiality stressh: compressive strength, the parameter such as poisson's ratio and modulus of elasticity of measuring rock under different confined pressure.

Only Seepage problems is considered in independent sand body.

(4) shallow drilling harm body numerical simulation analysis

Finite element method is method for numerical simulation conventional in field of engineering technology at present.The basic thought of finite element method is that the territory that solves of problem is divided into a series of unit, only connects by node between unit.The amount to be asked of unit internal point can be tried to achieve by selected functional relation interpolation by cell node amount.Because cell configuration is simple, is easy to set up equation between node amount by equilibrium relation or energy, then unit equation " group collection " is formed overall Algebraic Equation set together, can to solving equations after counting fringe conditions.

Seepage theory: finite element method solves the method for Seepage problems and dependent equation is:

The discretization of generalized Darcy's law, fundamental equation, problem, the finite elements form of three-dimensional porous medium fluid-structure coupling system.

The fundamental equation of three dimensional elastic dynamics is:

The equation of motion:

σ _{ij, j}+ f _i-ρ u _{i, tt}-μ u _i,t=0 (in Ω territory)

Geometric equation:

${\mathrm{\ϵ}}_{ij}=\frac{1}{2}(u_{i,j}+u_{j,i})$ (in Ω territory)

Physical equation:

σ _ij＝D _ijklε _kl

Fringe conditions:

(at S ^uon border)

(at S ^σon border)

Primary condition

U _i(x, y, z, 0)=u _i(x, y, z) (in Ω territory)

U _i,t(x, y, z, 0)=u _i,t(x, y, z) (in Ω territory)

In formula, ρ is mass density, and μ is damped coefficient, u _iand u _i,tbe respectively speed and the acceleration in i direction.

Comprehensively above-mentioned, the finite element solving equation that can obtain porous media fluid-structure coupling system is:

$\left[\begin{array}{cc}M& 0\\ 0& 0\end{array}\right]\left[\begin{array}{c}\stackrel{\·\·}{a}\\ p\end{array}\right]+\left[\begin{array}{cc}C& 0\\ K_p^T& S\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]+\left[\begin{array}{cc}K& -K_p\\ 0& H\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]=\left[\begin{array}{c}{F}_s\\ F_f\end{array}\right]$

A, mud shale layer numerical simulation analysis:

Levels position is sand layers, and position, intermediate layer is mud shale layer, and obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.Employing crack, mud shale layer bit stream field stream in model, arranges seam surface roughness coefficient.After mud shale immersion, its cohesive strength and angle of internal friction have and reduce significantly, and when injection pressure pressure is greater than mud shale layer fracture pressure, mud shale bedding opens expansion, until pressure is less than mud shale bedding initial cracking pressure.In the region that mud shale bedding is opened due to Pressure Drop, formation shallow-layer cover is damaged harm body.

Adopt free tetrahedron mesh generation model, by finite element analysis computation, obtain mud shale bedding splayed condition and shallow-layer cover damage harm body pressure distribution situation by modeling software.B, independent sand body numerical simulation analysis:

There is an independently sand body in the middle of stratum, shape approximation is Elliptic Cylinder shape, and permeability, the degree of porosity of independent sand body are all greater than surrounding formation, have independently modulus of elasticity.Obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.In model, flow field adopts darcy flow, and independent sand body and overall stratum arrange different permeabilities, degree of porosity, modulus of elasticity.Adopt free tetrahedron mesh generation model, through finite element analysis computation, obtain shallow-layer cover by modeling software and damage harm body pressure distribution situation.

The present invention has following beneficial effect: multiple block applies harm bodies of casing failure of shallow layer of close well spacing recognition technology construction more than 300 mouth wells, achieve significant effect, shallow-layer harm body identification prediction rate of accuracy reached is to 100%, the complicated incidence 1.67% of accident, drilling success reaches 100%, occur, for shallow-layer Tao Sun district safety drilling provides powerful guarantee without blowout out of control.

Detailed description of the invention:

This method for recognizing harm bodies of casing failure of shallow layer of close well spacing comprises the following steps:

Method for recognizing harm bodies of casing failure of shallow layer of close well spacing forms Analysis on Mechanism by shallow drilling harm body, geostatic stress prediction is tested with calculating and rock mechanics parameters, according to target area Geologic Structure Feature, sand-body distribution situation, well logging and log data, set up survey region geological model, and determine corresponding fringe conditions, use method for numerical simulation, predict geopressure abnormal conditions and reservoir stress distribution situation, identification object region drilling well harm body, and determine harm body influence basin, formulate drilling well countermeasure on this basis:

(1) determine that shallow-layer cover damages high nip pressures source, determine there is harm body thus:

After A, shallow-layer cover damages, water injection well is long-term toward the water filling of shallow-layer well section;

B, bottom oil layer high-pressure oil gas, by annular space in sleeve pipe, leak outside at shallow-layer cover damage point and enter upper formation;

C, understratum high-pressure oil gas are migrated to top by the sleeve pipe external space;

(2) calmodulin binding domain CaM Geologic Structure Feature, sand-body distribution situation, determine whether there is Reservoir Body, determines to there is harm body thus;

(3) shallow drilling harm body forms Analysis on Mechanism:

By coring in the past, the data such as density log carried out testing and testing.

A, mud shale layer shallow drilling harm body

Submerging test perpendicular to stratum bedding: the change utilizing X-Ray to detect water saturation in rock core is the technology of current comparative maturity, the position of water can be judged according to the X-Ray value before and after rock sample immersion, again by the time of measuring, just can calculate the immersion speed of mud stone, from result of the test: the immersion parameter of mud stone: mud stone immersion intensity, immersed depth and immersion speed, the impact of the main difference by cap rock pore pressure.

Along the interface submerging test of mud shale bedding: edge is perpendicular to direction, mud stone bedding interface and the submerging test along direction, mud stone bedding interface, the immersion speed describing mud stone slows down with the increase of soaking time, until immersion speed is zero, immersion speed and immersed depth are the function of difference between reservoir pre ssure and injection pressure, pressure reduction is larger, immersion speed and immersed depth also larger;

Mud stone water content is on the impact of its mechanical characteristic: the size of its cohesive strength of dissimilar mud shale and angle of internal friction has very big difference, but after immersion, its cohesive strength and angle of internal friction have and reduce significantly, and slope of a curve size description rock sample is to the sensitivity of immersion;

Mud shale drilling well harm body formation mechenism: injection pressure exceedes the fracture pressure of mud shale layer, and water enchroachment (invasion) scope is fracture length and length of flooding sum;

Crack initiation model: Terzaghi pattern, Shi Difen pattern, yellow flourish cup pattern;

Horizontal joint crack initiation pattern: when water injection pressure exceedes horizontal joint initial cracking pressure, the first crack initiation of mud shale layer, forms horizontal fracture, and Reservoir Fluid, form shallow drilling harm body;

B, independent sand body shallow drilling harm body

Geostatic stress derive from remaining palaeo-tectonic stress, stratum on cover water pressure gradient etc. in gravity, the motion collision of continental plate, stratum.Therefore geostatic stress is the internal stress of objective reality in subterranean body.In the rock mass of underground, there are three orthogonal main geostatic stress on direction, namely to be conducted oneself with dignity the main geostatic stress σ H of vertical geostatic stress σ v and two horizontal direction caused and σ h by rock mass.Generally, three main stress bares are unequal.

Geostatic stress computation model:

Vertical geostatic stress computation model:

Switzerland geologist Heim thinks that vertical geostatic stress σ v is caused by superstratum gravity, and it changes along with density of earth formations and the degree of depth, and therefore density available well-log information obtains vertical geostatic stress:

${\mathrm{\σ}}_v={\∫}_0^H\mathrm{\ρ}\left(h\right)\·g\·dh---(3-1)$

In formula: h is stratum buried depth; The function that ρ (h) changes with depth of stratum h for density of earth formations; G is acceleration of gravity.

Flatly stress calculation model: Jin Nike pattern, Mattews and Kelly model, Terzaghi model, Anderson model, Neberry model, two are to the ground stress model such as not

Suppose that stratum extrudes the original place minimum principal stress drawn to one direction, unidirectionally extruded result is exactly that stratum is in one direction by tectonic stress effect, and another direction there is no tectonic stress, but in fact majority of case is really not so, tectonic stress exists in all directions all substantially, and be unequal, the flourish cup professor of the Huang of University of Petroleum has drawn the relational expression of following expression geostatic stress size on Research foundation for many years:

${\mathrm{\σ}}_H=(\frac{{\mathrm{\μ}}_s}{1-{\mathrm{\μ}}_s}+\mathrm{\β})({\mathrm{\σ}}_v-{\mathrm{\αP}}_p)$

Geostatic stress result of calculation: use density log data and degree of depth data, each degree of depth geostatic stress value can be obtained.

Rock mechanics parameters is tested:

Test for tensile strength: measure tensile strength of rock.

Single shaft and triaxiality stressh: compressive strength, the parameter such as poisson's ratio and modulus of elasticity of measuring rock under different confined pressure.

Only Seepage problems is considered in independent sand body.

(4) shallow drilling harm body numerical simulation analysis

Finite element method is method for numerical simulation conventional in field of engineering technology at present.The basic thought of finite element method is that the territory that solves of problem is divided into a series of unit, only connects by node between unit.The amount to be asked of unit internal point can be tried to achieve by selected functional relation interpolation by cell node amount.Because cell configuration is simple, is easy to set up equation between node amount by equilibrium relation or energy, then unit equation " group collection " is formed overall Algebraic Equation set together, can to solving equations after counting fringe conditions.

Seepage theory: finite element method solves the method for Seepage problems and dependent equation is:

The discretization of generalized Darcy's law, fundamental equation, problem, the finite elements form of three-dimensional porous medium fluid-structure coupling system.

The fundamental equation of three dimensional elastic dynamics is:

The equation of motion:

σ _{ij, j}+ f _i-ρ u _{i, tt}-μ u _i,t=0 (in Ω territory)

Geometric equation:

${\mathrm{\ϵ}}_{ij}=\frac{1}{2}(u_{i,j}+u_{j,i})$ (in Ω territory)

Physical equation:

σ _ij＝D _ijklε _kl

Fringe conditions:

(at S ^uon border)

(at S ^σon border)

Primary condition

U _i(x, y, z, 0)=u _i(x, y, z) (in Ω territory)

U _i,t(x, y, z, 0)=u _i,t(x, y, z) (in Ω territory)

In formula, ρ is mass density, and μ is damped coefficient, u _iand u _i,tbe respectively speed and the acceleration in i direction.

Comprehensively above-mentioned, the finite element solving equation that can obtain porous media fluid-structure coupling system is:

$\left[\begin{array}{cc}M& 0\\ 0& 0\end{array}\right]\left[\begin{array}{c}\stackrel{\·\·}{a}\\ p\end{array}\right]+\left[\begin{array}{cc}C& 0\\ K_p^T& S\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]+\left[\begin{array}{cc}K& -K_p\\ 0& H\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]=\left[\begin{array}{c}{F}_s\\ F_f\end{array}\right]$

A, mud shale layer numerical simulation analysis:

Levels position is sand layers, and position, intermediate layer is mud shale layer, and obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.Employing crack, mud shale layer bit stream field stream in model, arranges seam surface roughness coefficient.After mud shale immersion, its cohesive strength and angle of internal friction have and reduce significantly, and when injection pressure pressure is greater than mud shale layer fracture pressure, mud shale bedding opens expansion, until pressure is less than mud shale bedding initial cracking pressure.In the region that mud shale bedding is opened due to Pressure Drop, formation shallow-layer cover is damaged harm body.

Adopt free tetrahedron mesh generation model, by finite element analysis computation, obtain mud shale bedding splayed condition and shallow-layer cover damage harm body pressure distribution situation by modeling software.B, independent sand body numerical simulation analysis:

There is an independently sand body in the middle of stratum, shape approximation is Elliptic Cylinder shape, and permeability, the degree of porosity of independent sand body are all greater than surrounding formation, have independently modulus of elasticity.Obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.In model, flow field adopts darcy flow, and independent sand body and overall stratum arrange different permeabilities, degree of porosity, modulus of elasticity.Adopt free tetrahedron mesh generation model, through finite element analysis computation, obtain shallow-layer cover by modeling software and damage harm body pressure distribution situation.

(5) shallow drilling harm body identification and prediction of formation pressure engineer applied:

A, southern two height 173-152 wellblocks, district

Pressure source is water 131 and water 231 well, is analyzed by geologic structure, and determine that southern two height 173-152 wellblocks, district are independent sand body harm body, inject fluid and directly enter sand body, progressively store, pressure raises gradually and spreads, and causes shallow-layer sand body to form abnormal pressure.Entity in model, stress-strain part hypothesis stratum is linear elasticity, and border arranges middle setting bottom surface fixed constraint, and its lap is set to initial stress border by geostatic stress value.In model, flow field simulation part adopts Darcy's law, arranging upper and lower aspect is barrier bed, peripheric surface is set to far field formation pressure, Thief zone in sand body, the hyposmosis of surrounding barrier bed, the pressure boundary condition of adjustment pressure source, makes the pressure monitoring value error of the forecast pressure value in abnormal pressure district and infill well close, calculates stress and the seepage pressure of each node in sand body.Set up region indirect fluid-solid coupling analytical model.Adopt free tetrahedron mesh generation model, 5% is less than for definite condition with the monitoring pressure value error of the strata pressure value of prediction and infill well, by finite element simulation calculation, identify target area drilling well harm body, and determine just to go out to endanger body influence basin and pressure size.

B, middle 71-p031 wellblock:

Pressure source is middle 7-p10 well, is analyzed by geologic structure, determines that middle 71-p031 wellblock is double break layer barrier structure, injects fluid and is subject to fault barrier, higher-pressure region is confined between tomography.Analyze mechanism and Pressure distribution range that fault barrier forms overpressure area.Entity in model, hypothesis stratum, stress-strain portion is linear elasticity, arranges two tomographies, and the mechanics parameter of tomography is different from sand layers mechanics parameter, and border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.In model, flow field simulation part adopts Darcy's law, and arranging upper and lower aspect is barrier bed, tomography impervious bed, and far field boundary is strata pressure.Set up region indirect fluid-solid coupling analytical model.Adopt free tetrahedron mesh generation model, by finite element analysis computation, identify target area drilling well harm body, and determine harm body influence basin and pressure size.

C, western 2 fault block height 429-27 wellblocks:

Two pressure sources, are analyzed by geologic structure, and western 2 fault block height 429-27 wellblock shallow-layer harm bodies are mainly distributed in tender two sections of bottom mud shale layers, near Faults.On east-west, there are three gradients, isohypse 765-775m in this region, the gradient is large, more precipitous, then enters flat zone, increases again in the 780-790m degree of depth gradient, there are two ridges at isohypse 775m and 780m position.There are two pressure sources, when injection pressure exceedes overlying formation pressure, fluid invades along mud shale bedding, and along stress low value area extension, along with blocking of pressure loss and tomography, crack no longer extends, and forms partial high pressure harm body.First model adopts structure mechanics analysis, supposes that stratum is linear elasticity, and border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value, analyzes the STRESS VARIATION that this geologic structure causes.Set up region indirect fluid-solid coupling analytical model.Adopt free tetrahedron mesh generation model, by finite element analysis computation, identify target area drilling well harm body, and determine just to go out to endanger body influence basin and pressure size.

D, apricot 12-4-p3712 wellblock:

Pressure source is apricot 12-4-the third 371, analyzed by geologic structure, apricot 12-4-p3712 wellblock shallow-layer harm body is mainly distributed in tender two sections of bottom mud shale layers, and horizontal bedding bedding is grown, there is 1 pressure source, when injection pressure exceedes overlying formation pressure, form crack, fluid invades along mud shale bedding, along with depth of invasion increases, pressure loss increases, and crack stops extending, and forms partial high pressure harm body.Set up physical model, entity in model, hypothesis stratum, stress-strain portion is linear elasticity, and border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value.Flow field employing crack stream in model, seam face arranges function of pressure drop, sets up region indirect fluid-solid coupling analytical model.Adopt free tetrahedron mesh generation model, by finite element analysis computation, identify target area drilling well harm body, and determine just to go out to endanger body influence basin and pressure size.Middle 7-10 well found 242 meters of bad breaks in 1975, and enforcement in 1981 is scrapped.In 1993, middle 7-more 10 wells found that shallow-layer (206-351 rice) leaks outside, within 1997, find 206 meters of bad breaks.High 145-37 well, high 145-373 well find 183 meters of casing-brokens in May, 2000.Above-mentioned four mouthfuls of wells are once long-term toward the water filling of shallow-layer (183-242 rice) well section, and middle 7-more 10 wellblock east-west directions grow 2 tomographies, sandstone is subject to fault barrier, and higher-pressure region is confined between tomography.Form shallow-layer harm body.Due to middle 7-more 10 wells obtain casing damage types for leaking outside, therefore think that this well is form the Major Stressors of higher-pressure region, its excess-three mouth well is secondary pressure source.By to harm bodies of casing failure of shallow layer of close well spacing identification, determine that harm body border should 7-10, middle 7-be more 10 in distance, within high 145-37,250 meters, 373 well, the degree of depth is at 160-260 rice, and pressure is at 1.55-1.1.75g/cm3.For the 6 mouthful wells of cloth on harm body, by taking different to increase the weight of well depth and density design, suitably increase dark, lower protective casing, former well pressure release under top layer, adopt and avoid cover around barrier orientation and damage the countermeasures such as harm body, whole drilling well success.

Claims (1)

1. a method for recognizing harm bodies of casing failure of shallow layer of close well spacing, the method comprises the following steps:

Method for recognizing harm bodies of casing failure of shallow layer of close well spacing forms Analysis on Mechanism by shallow drilling harm body, geostatic stress prediction is tested with calculating and rock mechanics parameters, according to target area Geologic Structure Feature, sand-body distribution situation, well logging and log data, set up survey region geological model, and determine corresponding fringe conditions, use method for numerical simulation, predict geopressure abnormal conditions and reservoir stress distribution situation, identification object region drilling well harm body, and determine harm body influence basin, formulate drilling well countermeasure on this basis:

(1) determine that shallow-layer cover damages high nip pressures source, determine there is harm body thus:

After A, shallow-layer cover damages, water injection well is long-term toward the water filling of shallow-layer well section;

B, bottom oil layer high-pressure oil gas, by annular space in sleeve pipe, leak outside at shallow-layer cover damage point and enter upper formation;

C, understratum high-pressure oil gas are migrated to top by the sleeve pipe external space;

(2) calmodulin binding domain CaM Geologic Structure Feature, sand-body distribution situation, determine whether there is Reservoir Body, determines whether there is harm body thus;

(3) shallow drilling harm body forms Analysis on Mechanism:

By coring in the past, density log data carried out testing and testing;

A, mud shale layer shallow drilling harm body:

Submerging test perpendicular to stratum bedding: the change utilizing X-Ray to detect water saturation in rock core is the technology of current comparative maturity, the position of water can be judged according to the X-Ray value before and after rock sample immersion, again by the time of measuring, just can calculate the immersion speed of mud stone, from result of the test: the immersion parameter of mud stone: mud stone immersion intensity, immersed depth and immersion speed, the impact of the main difference by cap rock pore pressure;

Along the interface submerging test of mud shale bedding: edge is perpendicular to direction, mud stone bedding interface and the submerging test along direction, mud stone bedding interface, the immersion speed describing mud stone slows down with the increase of soaking time, until immersion speed is zero, immersion speed and immersed depth are the function of difference between reservoir pre ssure and injection pressure, pressure reduction is larger, immersion speed and immersed depth also larger;

Mud stone water content is on the impact of its mechanical characteristic: the size of its cohesive strength of dissimilar mud shale and angle of internal friction has difference, but after immersion, its cohesive strength and angle of internal friction have reduction, and slope of a curve size description rock sample is to the sensitivity of immersion;

Mud shale drilling well harm body formation mechenism: injection pressure exceedes the fracture pressure of mud shale layer, and water enchroachment (invasion) scope is fracture length and length of flooding sum;

Crack initiation model: Terzaghi pattern, Shi Difen pattern, yellow flourish cup pattern;

Horizontal joint crack initiation pattern: when water injection pressure exceedes horizontal joint initial cracking pressure, the first crack initiation of mud shale layer, forms horizontal fracture, and Reservoir Fluid, form shallow drilling harm body;

B, independent sand body shallow drilling harm body:

Geostatic stress derive from remaining palaeo-tectonic stress, stratum on cover water pressure gradient in gravity, the motion collision of continental plate, stratum; Therefore geostatic stress is the internal stress of objective reality in subterranean body; In the rock mass of underground, there are three orthogonal main geostatic stress on direction, namely to be conducted oneself with dignity the main geostatic stress σ H of vertical geostatic stress σ v and two horizontal direction caused and σ h by rock mass, these three main stress bares are unequal;

Geostatic stress computation model:

Vertical geostatic stress computation model:

Switzerland geologist Heim thinks that vertical geostatic stress σ v is caused by superstratum gravity, and it changes along with density of earth formations and the degree of depth, and therefore density available well-log information obtains vertical geostatic stress:

${\mathrm{\σ}}_v={\∫}_0^H\mathrm{\ρ}\left(h\right)\·g\·dh---(3-1)$

In formula: h is stratum buried depth; The function that ρ (h) changes with depth of stratum h for density of earth formations; G is acceleration of gravity;

Flatly stress calculation model: Jin Nike pattern, Mattews and Kelly model, Terzaghi model, Anderson model, Neberry model, two are to the ground stress model such as not;

Suppose that stratum extrudes the original place minimum principal stress drawn to one direction, unidirectionally extruded result is exactly that stratum is subject to tectonic stress effect in one direction, and another direction does not have tectonic stress, and tectonic stress all exists in all directions, and be unequal, the relational expression of geostatic stress size:

${\mathrm{\σ}}_H=(\frac{{\mathrm{\μ}}_s}{1-{\mathrm{\μ}}_s}+\mathrm{\β})({\mathrm{\σ}}_v-{\mathrm{\αP}}_p)$

Geostatic stress result of calculation: use density log data and degree of depth data, each degree of depth geostatic stress value can be obtained; Rock mechanics parameters is tested:

Test for tensile strength: measure tensile strength of rock;

Single shaft and triaxiality stressh: measure the compressive strength of rock under different confined pressure, poisson's ratio and modulus of elasticity parameter; Only Seepage problems is considered in independent sand body;

(4) shallow drilling harm body numerical simulation analysis:

Finite element method is method for numerical simulation conventional in field of engineering technology at present, and the basic thought of finite element method is that the territory that solves of problem is divided into a series of unit, only connects by node between unit; The amount to be asked of unit internal point can be tried to achieve by selected functional relation interpolation by cell node amount; Because cell configuration is simple, is easy to set up equation between node amount by equilibrium relation or energy, then unit equation " group collection " is formed overall Algebraic Equation set together, can to solving equations after counting fringe conditions;

Seepage theory: finite element method solves the method for Seepage problems and dependent equation is:

The discretization of generalized Darcy's law, fundamental equation, problem, the finite elements form of three-dimensional porous medium fluid-structure coupling system;

The fundamental equation of three dimensional elastic dynamics is:

The equation of motion:

σ _{ij, j}+ f _i-ρ u _{i, tt}-μ u _i,t=0 (in Ω territory)

Geometric equation:

${\mathrm{\ϵ}}_{ij}=\frac{1}{2}(u_{i,j}+u_{j,i})$ (in Ω territory)

Physical equation:

σ _ij＝D _ijklε _kl

Fringe conditions:

(at S ^uon border)

(at S ^σon border)

Primary condition

U _i(x, y, z, 0)=u _i(x, y, z) (in Ω territory)

U _i,t(x, y, z, 0)=u _i,t(x, y, z) (in Ω territory)

In formula, ρ is mass density, and μ is damped coefficient, u _iand u _i,tbe respectively speed and the acceleration in i direction;

Comprehensively above-mentioned, the finite element solving equation that can obtain porous media fluid-structure coupling system is:

$\left[\begin{array}{cc}M& 0\\ 0& 0\end{array}\right]\left[\begin{array}{c}\stackrel{\·\·}{a}\\ p\end{array}\right]+\left[\begin{array}{cc}C& 0\\ K_p^T& S\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]+\left[\begin{array}{cc}K& -K_p\\ 0& H\end{array}\right]\left[\begin{array}{c}a\\ p\end{array}\right]=\left[\begin{array}{c}{F}_s\\ F_f\end{array}\right]$

A, mud shale layer numerical simulation analysis:

Levels position is sand layers, and position, intermediate layer is mud shale layer, and obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value; Employing crack, mud shale layer bit stream field stream in model, arranges seam surface roughness coefficient; After mud shale immersion, its cohesive strength and angle of internal friction have reduction, and when injection pressure pressure is greater than mud shale layer fracture pressure, mud shale bedding opens expansion, until pressure is less than mud shale bedding initial cracking pressure; In the region that mud shale bedding is opened due to Pressure Drop, formation shallow-layer cover is damaged harm body;

Adopt free tetrahedron mesh generation model, by finite element analysis computation, obtain mud shale bedding splayed condition and shallow-layer cover damage harm body pressure distribution situation by modeling software;

B, independent sand body numerical simulation analysis:

There is an independently sand body in the middle of stratum, shape is Elliptic Cylinder shape, and permeability, the degree of porosity of independent sand body are all greater than surrounding formation, have independently modulus of elasticity; Obtain material parameter and geostatic stress value by test in early stage and experiment, border arranges middle setting bottom surface fixed constraint, and its lap is set to stress boundary by geostatic stress value; In model, flow field adopts darcy flow, and independent sand body and overall stratum arrange different permeabilities, degree of porosity, modulus of elasticity; Adopt free tetrahedron mesh generation model, through finite element analysis computation, obtain shallow-layer cover by modeling software and damage harm body pressure distribution situation.