Horizontal Openhole Gravel Packing in a Depleted and Heterogeneous Reservoir

摘要

Open-hole gravel packing in vertical/conventional wells is anaccepted sand exclusion method that has not gained wide andrapid application in horizontal wells. The reason is largely dueto sand placement challenges in the horizontal drain that couldlead to premature sand screen-out. Consequently, manyoperators are skeptical gravel packing horizontal wells sincefailure could probably result in enormous capital risk. In theNiger Delta, about 70 % of the hydrocarbon-bearing reserveslie in shallow unconsolidated reservoirs where the sonic transittime vary between 110 to 140 us/ft. Production from theseintervals has proven record of sand threats to operating cost,well integrity, surface facilities and production sustenance.The challenge is to complete wells in these reservoirs withsand exclusion materials that would guarantee full life-cycleproduction performance.Early horizontal wells in the region were completedwith stand-alone screens, but recently, the expandable sandscreen (ESS) took a leading edge. Though the ESS has ahigher inflow area compared to other screens, its high cost,lack of full-bore expansion and the required lead-timecontinue to raise concerns especially when considered forapplications in brown field development where well potentialand reserve rewards are low. In response to these concerns, in2002, openhole gravel packing (OHGP) in a horizontal wellwas investigated and considered as an alternative sandexclusion option in Shell Petroleum Development Company(SPDC). The trial candidate, the Obigbo-North QWSB-3 wasselected and successfully completed as the first horizontalOHGP in SPDC using the alpha-beta wave concept.Based on simulation results, about 9237 lbm of sand wasplanned for placement in 1000-ft of 6.0-in hole size, however,the actual sand pumped was about 10830 lbm. This representsan estimate of 6.25-in drain hole size. The application savedover $0.3 million when compared to the cost of using ESS.For the Eastern asset team that drills an average of 12 wellsannually, an annual projected completion cost-saving of some$3.6 million is achievable.Based on the initial production testing, Obigbo-NorthWell QWSB-3 tested 3250 BOPD with a productivity index(PI) of 130 bbl/(psi-D). Baseline Memory Production LoggingTool (MPLT) logging showed that the entire drain sectioncompleted on the clean sand member had effective inflow intothe linerbore. In addition to establishing confidence in theapplication and performance efficacy of OHGP, this trial andthe significant cost-savings will engender a paradigm shift tohorizontal well sand control. In this presentation, we will sharesome data and results based on field experiences, challengesand new understanding.