History of Managing Productivity Issues Due to Fines Migration in a Malaysian Oil Field Offshore Sarawak

Abstract

Field D (offshore Sarawak, Malaysia) first production was in 2012 from three wells, with a second phase of development in 2017 with the drilling of four wells. Severe productivity decline was seen in five of the seven wells, and numerous studies were completed to narrow in on the root causes. Several production enhancement techniques were executed on Phase 1 and Phase 2 wells, where learnings and results will be further shared. Prior to the drilling of six additional wells in Phase 3 (2020), additional detailed lab studies were undertaken, and new strategies were implemeted based on this were applied with encouraging results. The majority of the wells have downhole pressure gauges (PDG), and coupled with frequent well test data, PTA, and Nodal Analysis modeling Productivity Index, permeability thickness (kH), and Skin are able to be tracked over time. By trending these different productivity indicators, it became clear that formation damage was occurring in several wells with varying degrees of severity based on the performance of the reservoir layer being produced. Various formation damage mechanisms were assessed (scale, wax, asphaltenes, drilling & completion damage, fines migration), and based on the initial study it was determined that fines migration was likely the major issue. Historically, no sand was observed on the surface where monthly sand count reported has always been <1 pound per thousand bbl (pptb) which was supported by geomechanics, and sand failure tendency studies completed during development phase of the field. Hence, six of the seven Phase 1 and 2 wells were completed with cased and perforated strategy with no downhole sand control, with the other well completed as a highly deviated open hole standalone completion. The productivity declines were only experienced in the cased and perforated completions, which had much lower gross completed interval and thus experienced higher velocities near the wellbore. The main production enhancement strategy applied to date has been re-perforation (8 re-perforation jobs), with varying degrees of productivity improvement and duration of sustainability. Solid propellant technology was applied in one of the well and clearing of the perforation tunnels via through-tubing dynamic underbalance technique in two wells was applied and no major improvement in sustained production impact was observed. An acid stimulation was recently pumped for the first time in one well and the assessment details will be shared, and results of the pumping will be shared in detail. At the time of the paper, no post production results were available. Prior to the drilling of six Phase 3 wells in 2020, detailed lab studies to look at the impact of various drilling muds were assessed, and learnings were incorporated in the mud program. Critical velocity studies were completed, and learnings from this work such as well ramp-up strategy and normalized maximum production rates have been added to the well-by-well production strategy. Based on Phase 3 production data to date, application of these new learnings has resulted in no major productivity decline seen. The learnings from D field would benefit other operators by sharing the lessons learned on assessment of formation damage mechanisms, the results of the different type of production enhancements applied, and the successful mitigation strategies for future wells (lab assessment, mud strategy change, and production strategies to prevent plugging due to fines migration).