A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is est...A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is established by expanding the essential terms of the assumed stress field as polynomials in the natural coordinates of the element. The homogeneous equilibrium equations are imposed in a variational sense through the internal displacements which are also expanded in the natural coordinates, while the tractionfree conditions along the inclined side are satisfied exactly. The use of such special element in the finite element solution is shown to be highly accurate when only a very coarse element mesh is used for plates with V-shaped rounded notches or inclined sides.展开更多
Oil exploration and production,well stability,sand production,geothermal drilling,waste-water or CO_(2) sequestration,geohazards assessment,and EOR processes such as hydraulic fracturing,require adequate information a...Oil exploration and production,well stability,sand production,geothermal drilling,waste-water or CO_(2) sequestration,geohazards assessment,and EOR processes such as hydraulic fracturing,require adequate information about in-situ stresses.There are several methods for analyzing the magnitude and direction of in-situ stresses.The evaluation of tensile fractures and shear fractures in vertical oil and gas wellbores using image logs is one of these methods.Furthermore,when image logs are run in boreholes,they can be extremely costly and possibly stop the drilling.The data for this study were gathered from seven directional wells drilled into a strike-slip fault reservoir in southern Iran.Vertical stress,minimum horizontal stress,pore pressure,Poisson's ratio of formations,and 233 mud loss reporting points make up the entire data.This is the first time maximum horizontal stress direction has been calculated without referring to image log data.In addition,the points of lost circulation were categorized into natural and induced fracture.The results revealed that,the maximum horizontal stress direction of the reservoir was calculated at 65northeast-southwest.The error rate is roughly 10when comparing the results of this investigation to those obtained from the image log.The maximum horizontal stress direction is calculated precisely.In terms of tensile fracture pressure,the in-situ stress ratio identifies the safest as well as the most critical inclination and azimuth for each well.展开更多
In order to accurately calculate drilled trajectories,the method of quantitatively recognizing borehole trajectory models was provided,and a case analysis was conducted.Because the measurement-while-drilling data prov...In order to accurately calculate drilled trajectories,the method of quantitatively recognizing borehole trajectory models was provided,and a case analysis was conducted.Because the measurement-while-drilling data provide with measured values of tool-face angle besides inclination angle and azimuth angle,this paper presents the technological approach of recognizing borehole trajectory models based on tool-face angle.A universal tool-face angle equation was established based on the directional deflection mechanism of steerable drilling tools,and it can calculate the tool-face angles with characteristic parameters of various borehole trajectory models.Then,by evaluating the error between the theoretical values and the measured values of tool-face angle,the trajectory model most consistent with the actual well trajectory can be selected.The model recognition of borehole trajectory provides with the quantitative evaluation index and selection basis of survey calculation methods,which can avoid subjectively and randomly selecting the survey calculation method,and consequently improve the monitoring accuracy and reliability of borehole trajectory.展开更多
文摘A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is established by expanding the essential terms of the assumed stress field as polynomials in the natural coordinates of the element. The homogeneous equilibrium equations are imposed in a variational sense through the internal displacements which are also expanded in the natural coordinates, while the tractionfree conditions along the inclined side are satisfied exactly. The use of such special element in the finite element solution is shown to be highly accurate when only a very coarse element mesh is used for plates with V-shaped rounded notches or inclined sides.
文摘Oil exploration and production,well stability,sand production,geothermal drilling,waste-water or CO_(2) sequestration,geohazards assessment,and EOR processes such as hydraulic fracturing,require adequate information about in-situ stresses.There are several methods for analyzing the magnitude and direction of in-situ stresses.The evaluation of tensile fractures and shear fractures in vertical oil and gas wellbores using image logs is one of these methods.Furthermore,when image logs are run in boreholes,they can be extremely costly and possibly stop the drilling.The data for this study were gathered from seven directional wells drilled into a strike-slip fault reservoir in southern Iran.Vertical stress,minimum horizontal stress,pore pressure,Poisson's ratio of formations,and 233 mud loss reporting points make up the entire data.This is the first time maximum horizontal stress direction has been calculated without referring to image log data.In addition,the points of lost circulation were categorized into natural and induced fracture.The results revealed that,the maximum horizontal stress direction of the reservoir was calculated at 65northeast-southwest.The error rate is roughly 10when comparing the results of this investigation to those obtained from the image log.The maximum horizontal stress direction is calculated precisely.In terms of tensile fracture pressure,the in-situ stress ratio identifies the safest as well as the most critical inclination and azimuth for each well.
基金Supported by the China National Science and Technology Major Project(2017ZX05005-005)
文摘In order to accurately calculate drilled trajectories,the method of quantitatively recognizing borehole trajectory models was provided,and a case analysis was conducted.Because the measurement-while-drilling data provide with measured values of tool-face angle besides inclination angle and azimuth angle,this paper presents the technological approach of recognizing borehole trajectory models based on tool-face angle.A universal tool-face angle equation was established based on the directional deflection mechanism of steerable drilling tools,and it can calculate the tool-face angles with characteristic parameters of various borehole trajectory models.Then,by evaluating the error between the theoretical values and the measured values of tool-face angle,the trajectory model most consistent with the actual well trajectory can be selected.The model recognition of borehole trajectory provides with the quantitative evaluation index and selection basis of survey calculation methods,which can avoid subjectively and randomly selecting the survey calculation method,and consequently improve the monitoring accuracy and reliability of borehole trajectory.
