Detecting Complexity of Karstified Limestone Sequence Using Well and Seismic Data for Drilling Optimization in Tangguh Fields, West Papua

The Tangguh well drilling spent for almost $ 100-200 million dollars for one offshore well in frontier area of West Papua. Historically, Non Productive Time (NPT) during the initial developments drilling campaign was estimated at 17% (c.$80 million), which identified as drilling surprises from almost natural complex geology related and 80 % of the total were contributed from highly karstified limestone in Faumai Formation. It�s mainly because of stuck pipe or wireline tool failure due to difficult penetration into thick hard dolostones, rubble faults zone, and total losses circulation. Current 3D seismic conventional has inadequate seismic quality to image these complex overburdens due to recording absorption by overlying thick massive and karstified LS of Kais and Faumai Formations. In fact, geology hazards cannot be avoided totally, therefore risks identification in Faumai Formation, contingency or mitigation plans should be well defined and described to reduce NPT that could impacts to the success drilling performances with null incidents while drilling operation in future. Recently, none comprehensive Faumai geology hazards study had been done and need to build an integrated analysis using best practice of a risk cube geology hazard modeling base on detail well data and seismic overburden enhancement imaging evaluation for the upcoming Tangguh wells optimization. This study addressed the root causes of those geology hazards using integrated subsurface data assessments focused in Faumai Formation interval, to detect geology complexity within this formation from: thick hard dolostones distribution, rubble faults mapping, density, and orientation, and also defined geometry of its karstified limestone in losses circulation zone. The final result was expected to be used to guide the subsurface and drilling teams to reduce the probability to occur or to lessees the impact possible of those potential drilling hazards