Method for predicting well reliability by computer simulation

A computer-implemented method for modeling a geomechanical system, the geomechanical system having a subsurface rock formation containing a hydrocarbon reservoir, comprising:

• defining physical boundaries for the geomechanical system, wherein the geomechanical system comprises a hydrocarbon reservoir and a wellbore casing as members of the geomechanical system;
• creating a map-based geologic model from well logging data and seismic data, the map-based geologic model defining a three-dimensional, digital representation of the geomechanical system;
• deriving a finite element-based global geomechanical model from the map-based geologic model;
• deriving a complimentary finite element-based submodel from the global geomechanical model to simulate the effects of changes in pore pressure on stress in the rock formation and wellbore casing to determine the an effective strain (εeff) in a member of the geomechanical system at selected nodes in the geomechanical system that takes into account a compaction strain (εc) and at least two out-of-plane shear strains (γ1-3 , γ2-3);
• determining a critical effective strain criteria (εeff cr) for a member of the geomechanical system based upon analysis of a history of well failures experienced in the geomechanical system and using a probabilistic method based upon a measure of casing kink angle or dogleg severity;
• comparing (1) the effective strain (εeff) at the selected node, with (2) the critical effective strain criteria (εeff cr) to determine if the effective strain (εeff) exceeds the critical effective strain criteria (εeff cr).

A computer-implemented method for predicting wellbore failure in a geomechanical system, the geomechanical system having a subsurface rock formation containing a hydrocarbon reservoir, comprising:

• defining physical boundaries for the geomechanical system, wherein the geomechanical system comprises a hydrocarbon reservoir and a wellbore casing;
• acquiring pore pressure history from production activities of multiple wells existing within the physical boundaries;
• acquiring mechanical properties of rock formations and wellbore casing within the physical boundaries;
• creating a finite element mesh representing the geomechanical system, the mesh defining a plurality of nodes representing points in space, each point having potential displacement in more than one direction, wherein the mesh provides a positive value for any rock formations having a zero thickness as derived from subsurface data in order to create volume for each rock formation;
• mapping pore pressure within the geomechanical system at a first time for nodes within the mesh;
• mapping pore pressure within the geomechanical system at a plurality of additional times to correspond to the nodes within the mesh, wherein the mesh provides a positive value for any rock formations having a zero thickness as derived from subsurface data in order to create volume for each rock formation;
• running a geomechanical simulation for the geomechanical system to simulate the effects of changes in the at least one reservoir characteristic on stress in rock formations and wellbore casing within the physical boundaries to determine an effective strain (εeff) in a member of the geomechanical system at selected nodes in the reservoir, by considering a compaction strain (εc) and at least two out-of-plane shear strains (γ1-3 , γ2-3);
• determining a critical effective strain criteria (εeff cr) for a member of the geomechanical system from the compaction strain (εc) and out of plane shear strain (γ1-3 , γ2-3) using a probabilistic method based upon a measure of casing kink angle or dogleg severity;
• comparing (1) the effective strain (εeff) at a selected nodal point representing the approximate location of a well at a given depth within the physical boundaries, with (2) the critical effective strain criteria (εeff cr) to determine if the effective strain (εeff) exceeds the critical effective strain criteria (εeff cr);
• and
• determining which wells within the physical boundaries have an effective strain (εeff) that exceeds the effective strain criteria (εeff cr) at the given depth, thereby predicting wellbore failures;
• and
• creating a map of the physical boundaries for the geomechanical system demonstrating the approximate location of the wellbore failures.

A computer-implemented method for predicting wellbore failure in a geomechanical system comprising a hydrocarbon reservoir, the geomechanical system having a subsurface rock formation containing a hydrocarbon reservoir, comprising:

• selecting a strain criteria at which wellbores in the geomechanical system are predicted to fail based upon a history of wellbore failures experienced in the hydrocarbon reservoir;
• acquiring mechanical properties of rock formations and a wellbore casing within physical boundaries for the geomechanical system;
• creating a finite element mesh representing the geomechanical system, the mesh defining a plurality of nodes representing points in space, each point having potential displacement in more than one direction;
• wherein the mesh provides a positive value for any rock formations having a zero thickness as derived from subsurface data in order to create volume for each rock formation;
• mapping pore pressure within the geomechanical system at a first time for nodes within the mesh;
• mapping pore pressure within the geomechanical system at a plurality of additional times to correspond to the nodes within the mesh;
• running a geomechanical simulation to simulate the effects of changes in a selected reservoir characteristic on stress in rock formations within the hydrocarbon reservoir at a selected time and a selected wellbore area to generate a simulated wellbore strain;
• wherein generating the simulated wellbore strain comprises determining an effective strain (εeff) in a member of the geomechanical system at selected nodes in the reservoir, considering a compaction strain (εc) and at least two out of plane shear strains (γ1-3 , γ2-3) , based upon a measure of casing kink angle or wellbore dogleg severity, and the selected reservoir characteristic comprises at least one of pore pressure history, temperature history, permeability, porosity, and combinations thereof;
• comparing the simulated wellbore strain with the strain criteria to determine if the simulated wellbore strain exceeds the strain criteria, thereby predicting wellbore failure;
• and
• adjusting hydrocarbon reservoir management processes to militate against the predicted wellbore failure.