Successful Production Enhancement for Carbonate Gas Reservoirs by Under Balanced Coiled Tubing Drilling Using Production and Seismic Data

Abstract

This paper discusses the innovative method of production enhancement with under balanced coiled tubing drilling (UBCTD) by using production and seismic data to steer in carbonate gas reservoirs. Certain carbonate reservoirs lack of microfossils to identify the productive layers, which makes it challenging for UBCTD operation to steer in such reservoirs by just analyzing the cutting samples without real time logging. A new method is applied to place wells in porous and productive layers with the help of production and seismic data. During drilling, gas production is monitored in real time and analyzed with productivity index. Good production zone is identified with increasing productivity index and linked with acoustic impedance (AI) from seismic data which helps to steer in productive layers. Such approach helps UBCTD operation to identify and stay in the good production zone in real time, increasing the certainty of well placement due to carbonate reservoir heterogeneity and maximizing the production contribution from drilled footage. Wells can be drilled without cutting sample analysis or real time logging, reducing operation cost and risk of stuck logging tool. Overall, extended reservoir contact can be reached with minimum formation damage and therefore production is enhanced substantially. At the end of the UBCTD operation, production potential is assessed during the flowback to clean up drilling fluid. No further rigless stimulation job is required and wells can be put on production immediately after drilling completion. The benefits of such optimized method is evident in the outstanding gas production from the drilled wells. This provides an efficient alternative to enhance production from carbonate gas reservoirs with better economic feasibility.