Presented in this paper are the results and verification of field-and wellbore-scale large deformation, elasto-plastic, geomechanical finite element models of reservoir compaction and associated casing damage. The models were developed as part of a multidisciplinary team project to reduce the number of costly well failures in the diatomite reservoir of the South Belridge Field near Bakersfield, California. Reservoir compaction of high porosity diatomite rock induces localized shearing deformations on horizontal weakrock layers and geologic unconformities. The localized shearing deformations result in casing damage or failure. Twodimensional, field-scale finite element models were used to develop relationships between field operations, surface subsidence, and shear-induced casing damage. Pore pressures were computed for eighteen years of simulated production and water injection, using a three-dimensional reservoir simulator. The pore pressures were input to the two-dimensional geomechanical field-scale model. Frictional contact surfaces were used to model localized shear deformations. To capture the complex casing-cement-rock interaction that governs casing damage and failure, threedimensional models of a wellbore were constructed, including a frictional sliding surface to model localized shear deformation. Calculations were compared to field data for verification of the models.

Cc?@aht 199S. Sod! of Petroleum Engineers. lnc This paper was prepared fw presemtath at the SPEilSRM Eurc.ck '9SJheld in Trc+v5heim, Norway, S-10 July 199S, This paper Ws-seleeted for presentation by an SPS Program Committee foffowing review of infwmat!.m c.ntamed In an abstract submitted by the author(s) Ccotenls of the paper, as pmsentad, have not been rewewed by the %dety of Petroleum Engineers and are subjecf to correct!cm by the authcf (s). The malenal, as presented, dces not necessaoly reflect any positm of tfw %ciety of Petrc4eum Engineers, IIS ofhcers, or members Papers presented at SPE meetmgs are subjact to Publicatlcm rewew by Edtlor!al Commmees of Ihe SOcle!y of petroleum Engineers Electrcoic reprcduct!-an,distribution, or storage ot any Part of thm paper for commercial Furpeses tithout the wdtfen consent of the Society of Petroleum Engineers is prohibited Permissica 10 reprcdurn m print is restflcfed to an abstract of not more than XXI wads, iliustraticms may nOt be COPIed The abstract must contain conspicuous acknowledgment of where and by vhom lhe paper was presented Write Llbranan, SPE. PO. Sax S3SSSS. R!chardsc+!.TX 7SCKHS36, U. S.A., fax 01.972.952.9435 AbstractPresented in this paper are the results and verification of field and wellbore scale large deformation, elasto-plastic, geomechanical finite element models of reservoir compaction and associated casing damage. The models were developed as part of a multidisciplinary team project to reduce the number of costly well failures in the diatomite reservoir of the South Be[ridge Field near Bakersfield, California.Reservoir compaction of high porosity diatomite rock induces localized shearing deformations on horizontal weak-rock layers and geologic unconformities. The localized shearing deformations result in casing damage or failure. Two-dimensional, tieldscale finite element models were used to develop relationships between field operations, surface subsidence, and shearinduced casing damage. Pore pressures were computed for eighteen years of simulated production and water injection, using a three-dimensional reservoir simulator.The pore pressures were input to the two-dimensional geomechanical field scale model. Frictional contact surfaces were used to model localized shear deformations. To capture the complex casing-cement-rock interaction that governs casing damage and failure, three-dimensional models of a wellbore were constructed, including a frictional sliding surface to model localized shear deformation. Calculations were compared to field data for verification of the models.

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