Engineering and Operational Issues Associated with Commingled Drill Cuttings and Produced Water Re-injection Schemes

摘要

Current BP Group Environmental Expectations of zerorndischarge of oilfield waste to the environment by 2005 andrnreduction in land-fill disposal options are driving thernCompany towards innovative disposal schemes that offerrnattractive and significant environmental and operational costrnbenefits. One of the current BP initiatives is to merge thernsynergies of both produced water and drilling cuttings into arnsingle commingled re-injection scheme in the same well.rnMerging the two technologies for waste disposal in the samernformation in the same well becomes a very attractive option, ifrnthe well can be engineered and completed to meet the specificrnobjectives of disposing of large volumes of produced waterrnand periodic disposal of drill cuttings from in-fill wells. Thernmain advantages of such a disposal scheme are:rn1. Better assurance of fracture containment for disposal ofrnoil-contaminated cuttings.rn2. Reduced cost of both operations because of fewer wellsrnand reduced chemicals cost than would be required forrnseparate drill cuttings and produced water disposalrnschemes.rn3. Potential recovery of disposal cost with secondaryrnrecovery, if suitable targets are available.rnBP has successfully implemented commingled re-injectionrnof produced water and drill cuttings in the Wytch Farm andrnValhall fields. These commingled re-injection schemes werernimplemented to address urgent operational need to managerndrill cuttings disposal when only water injector wells orrnproducers were available. This paper addresses keyrnengineering issues and risks, which are being evaluated as partrnof an ongoing BP project to develop engineering guidelinesrnfor commingled produced water (PWRI) and drill cuttingsrn(DCRI) re-injection. The paper outlines synergies andrndifferences in current DCRI and PWRI processes and therndominant parameters that are likely to control successfulrncommingled re-injection process.