Dip Interpretation from Resistivity at Bit Images (RAB) Provides a New and EfficientMethod for Evaluating Structurally Complex Areas in the Cook Inlet, Alaska

摘要

Many of the producing fields in the Cook Inlet area of Alaskarnare found in tightly folded, asymmetric, fault bounded,rnanticlinal structures that are not easily imaged with modernrnseismic. Historically, exploration wells have been drilledrninitially on the crest of these features, only to find at totalrndepth that the bore holes had deviated off the crest and werernseveral thousand feet down dip from the initial structuralrnobjective. In Cook Inlet, where difficult hole conditionsrnprevail, a new approach to real time structural analysis wasrnneeded to evaluate complexly folded features as they werernbeing drilled.rnAcquisition of structural dips while drilling a potentiallyrncomplex structure was critical in evaluating the position of thernwell on the structure and steering it if necessary. Measurementrnwhile drilling (MWD), coupled with logging while drillingrn(LWD) provided the data necessary to enable a successfulrndrilling operation and well completion.rnThe Resistivity-at-the-Bit (RAB)* tool was used duringrndrilling to acquire resistivity measurements close to the bit.rnThese resistivity measurements were then used to producernimages and calculate dips similar to a Fullbore FormationrnMicroImager (FMI)*. Modifications to the structural modelrnwere continually made based on interpretations from the RABrnimages, allowing the bore hole to be steered towards arnpreferred structural position.rnFMI and RAB images and interpreted dips were compared in arnshallow interval to evaluate the quality of RAB data. Excellentrnagreement in measurements between the tools resulted in therncontinued use of RAB for the duration of the well.