Wireline formation testers are corrently widely used in openrnholes while through-casing formation testing is still in its earlyrnstage of application.rnIn this paper, a case history is presented where formationrnpressures are acquired through-casing in the Khuff deep gasrnformation. Considering the Khuff formation in Saudi Arabiarnand associated drilling difficulties, formation testing in openrnhole conditions can be quite challenging. In this field example,rnformation testing in an open hole was initially planned;rnhowever, drilling conditions did not permit open holernformation testing. Hence, a through-casing formation testerrnwas utilized for the first time in Saudi Arabia to obtainrnimportant formation pressure measurements to assess pressurernregimes in a reservoir with different layers. The throughcasingrnformation tester anchors itself within casing, sets arnpacker element, drills a hole in the casing and through therncement and formation, performs pressure testing and orrnsampling, reseals the hole, pressure tests the mechanical plugrnand then frees itself from the casing to move to next testingrninterval. One of the challenges of through-casing formationrntesters is cement integrity behind the casing. Cementrnevaluation logs were run prior to the formation tester run. Itrnwas found that cement was patchy across the zone of interest.rnThe through-casing formation tester was run over carefullyrnselected intervals, and nine holes were drilled and pluggedrnsuccessfully in three wireline runs. After the jobs, leak tests ofrn4000 psi differential were carried out and confirmed the casingrnintegrity.rnResults showed interesting pressure differences amongrndifferent layers with similar pressure trends observed in nearrnby wells. The operational challenges, observations andrnrecommendations for future applications are discussed in thisrnpaper.
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