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Use of Networked Geosteering Software for Optimum High-Angle/Horizontal Wellbore Placement: Two U.K. North Sea Case Histories
This paper presents two case histories that demonstrate therneffectiveness of an active geosteering approach usingrncomputer networking between rig site and operator office. Arnsatellite link was used to update well trajectory and LWD datarnin StrataSteer? geosteering software located within thernoperator’s asset group. This link provided the key advantagernof allowing subsurface staff to become an integral part of therngeosteering process.rnThe geosteering software enables a geological /rnpetrophysical model to be created based on offset well log datarnand seismic profiles. The LWD log responses are modeledrnalong the planned well trajectory and then compared to thernactual LWD log responses (gamma, multi-depth resistivity,rnneutron, and density). The responses are then used to adjustrnthe geological model and take geosteering decisions.rnThe amended geological situation enabled immediate andrnenhanced decision-making regarding adjustments to the wellrnpath in order to remain within the optimum reservoir zone.rnGood communication between all parties involved, bothrnonshore and offshore, undoubtedly contributed to the successrnof both operations.rnThe two example wells, “A” and “B”, present differentrnchallenges. In both cases, it was clear prior to drilling thatrnactive geosteering would be necessary. Well A was planned asrna horizontal oil producer. The vertical thickness of the payrnsection was estimated at 13 ft, and the bed dip was expected tornvary between 0 and 2 degrees in the direction of drilling.rnFollowing successful landing of the well, a total of 1300 ft ofrntarget reservoir was drilled using the geosteering software tornactively guide the well path. Production rates from this wellrnwere significantly above pre-drill expectations.rnThe objective in Well B, a deviated sidetrack, was to drillrnthrough four reservoir zones, two on either side of a majorrnfault. Recognition of the fault in real-time was critical due torndifferent reservoir thickness and bed dips across the fault andrnsignificant uncertainty regarding the position of the fault. Thernuse of geosteering software enabled the fault to be quicklyrnrecognized when it appeared — some 450 ft along hole earlierrnthan expected. The geological model was quickly revised andrnthe well path adjusted to optimize placement in the final tworntargets.
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