Some Advances in Near Wellbore Geomechanics

摘要

There has been substantial recent progress in couplingrngeomechanical effects to reservoir response, thus dramaticallyrnimproving representation of the consequences of rockrnresponse to pressure changes. New reserves have beenrnidentified from compaction. Injection geomechanics hasrngained an increase in interest due to its impact on thernreservoir, faults and well hardware. Changes inrntransmissibility are now seriously implemented in reservoirrnengineering tools with more attention directed at the presencernof compaction and dilatant bands around producers orrninjectors. Efforts are progressing to ensure adequate couplingrnbetween the local effects of the rock deformation near thernwellbore, as well as along faults or bedding planes, and thernevolving stresses and deformation in the reservoir.rnThis paper attempts to discuss current gaps inrnunderstanding the intricacies and details of coupling farfieldrndeformation to well completion. Examples are shown wherernreservoir compaction or dilatancy is explicitly coupled to nearwellborernbehavior, with specific application for assessing wellrnperformance and survivability. The analyses can use reservoirrnsimulations coupled with analytical predictions of stresses andrndeformations in individual simulator blocks. The predictedrnstresses and deformations form the boundary conditions forrnfinite element modeling that can focus in on the details aroundrnthe completion itself. This is in contrast to the currentrnapproaches that use explicit coupling of pressure andrndeformation in complete massive finite elementrnrepresentations, with refined gridding around the completion.rnThe intimate details of coupling reservoir deformation tornthe completion require more intensive consideration. Forrnexample, “How can the cement sheath be represented?” orrn“What are some of the constitutive considerations in the nearwellborernregion that impact integrity?” and “How is varyingrntransmissibility related to well integrity?” These issues arernconsidered. There are three goals:rn1. Start to recognize completion and productionrnmanagement practices that will improve completionrnlongevity and optimize well productivity.rn2. Identify reasonable methodologies for representing therncoupling between the completion and the reservoir,rnincluding yielded zones (dilatant and/or compactant),rncompaction bands with varying transmissibility, therncement sheath with or without a microannulus and thernmud cake.rn3. Delineate approximate methods that will adequatelyrnforecast completion distress and permeability impairmentrnwithout the necessity of expensive and time-consumingrndetailed finite element simulations.