Modelling of fines migration mechanisms in high permeability sands - impact on reservoir performance.
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Today the oil and gas industry suffers significant production losses due to fines migrations in high permeability sandstone formations or sand packs. During drilling, production or injection, fines migration continues to cause formation impairment resulting in oil and gas inflow reductions or injectivity resistance. The problem is further enhanced in mature reservoirs where increased water ingress and multiphase production aggravate the fines mobilisation. Proper fines management can optimise productivity, injectivity, safeguard facilities and reduce well maintenance cost. Today‘s core flood tests as part of risk assessment limit tests to single phase or at best two-phase oil/water flow. Meanwhile existing reservoir simulators have no facilities to analyse solid particles impact on productivity and injectivity. This research work presents the unique technique adopted to analyse fines migration mechanisms in a true multiphase environment. The methodologies adopted include studies of fines particle impacts on pressure drawdowns in several sensitivities of rock permeability, water cut, multiphase flow, liquid flow, porosity, fines grain size, and the rest of relevant rock and fluid properties performed using an appropriate Computational Fluid Dynamics (CFD) simulator. The resultant drawdown pressures were then used to back-calculate corresponding particle-damaged permeabilities using a conventional field approach. From the results obtained, detailed mapping of prevailing pore blocking mechanisms and corresponding permeability impairment profiles are presented as functions of operating conditions. The technique integrates the CFD and 3-D reservoir simulation concepts to define and quantify the effects of different operating conditions on discretised reservoir blocks. Among the major research outcomes are two developed particle-damaged absolute permeability models for multiphase and liquid flow conditions involving fines migration in porous media. The models were tested and validated using ten examples of field data with acceptable error margins in the majority of the cases. Contributions to knowledge include: i) new analysis of particle impact in multiphase and liquid flows, ii) integration of CFD with 3-dimensional reservoir simulator and iii) the developed particle-damaged models. Areas where more study is required include: a) dry gas CFD simulation, b) use of real rock (thin-section) pore structure scans as the computational mesh and c) adapting the application to EOR (enhanced oil recovery) operations such as steam injection, miscible fluid injection and others. These are highlighted as suggestions for further work to improve effectiveness of the developed advances towards better fines migration management. The research work is concluded with recommendations (supported by flow efficiency case studies) on contemporary innovations in fines management.