A Case Study of Drilling Optimization for Middle EastCarbonate Reservoir Using a Formation-Testing-While-Drilling Tool

摘要

Formation testing while drilling (FTWD) technologyintroduced in 2002 has been used primarily forapplications similar to wireline formation testers. Theseinclude formation pressure tests, gradient analysis,formation connectivity, differential depletion and flowbarrier detections. A largely untapped application forFTWD is drilling optimization, which has somewhatdifferent testing practices. Here it is desirable to obtainpressures as soon as possible and real-time test analysiscombined with other downhole drilling data like mudparameters, overbalance, weight on bit etc. enablesdrilling parameters to be adjusted to improve the rate ofpenetration (ROP) and make adjustments to thewellbore stability modeling literally while drilling.This paper reviews a Middle East case study in acarbonate gas reservoir. In this part of the fieldreservoir pressure was uncertain as a result of possiblecommunication with a high-pressure lower interval.Establishing the actual formation pressure was thereforea priority. By monitoring the FTWD pressure tests inreal-time it was possible to verify the quality andvalidity of each test. The test data was then used togradually change mud parameters. A composite logclearly indicated how decreasing annular pressuresresulted in an increase in ROP. The method of testingand the real-time monitoring results are reviewed andcompared with high resolution memory data from theFTWD tool, which confirmed the real-time validationof the test-data. Conclusions are drawn concerningdrilling applications and how such test data can be usedto improve the drilling process. Best practices fordesigning formation testing procedures while drillingare also reported.