Assessing the Capabilities of a Cased-hole Reservoir Analysis System in the Gulf of Thailand

摘要

The option of using a cased-reservoir analysis system as anrnalternative to traditional open-hole log analysis was tested as arnmethod to reduce drilling rig time. On a series of five wells inrnthe Gulf of Thailand, an integrated pulsed-neutron system thatrnmeasures Sigma, inelastic spectroscopy, neutron porosity andrndensity was used to drive the cased-hole analysis. Therncapabilities and accuracy of the cased-hole results wererncompared to open-hole porosities and water saturations.rnOne concern for cased-hole logging is accuracy in thisrnwell-completion environment. These wells are completed asrnmonobores with 2 7 /8-inch tubing cemented directly into thern6 1 /8-inch open hole (no well casing). Initially, the pulsed-neutronrnporosity coefficients for 5?-inch casing were usedrnwith reasonable accuracy. To increase the porosity accuracy,rnthe data from this test served as input to an artificial neuralrnnetwork for determining porosity coefficients in this specificrnborehole environment.rnThe project consisted of 12,099 feet of log data includingrn30 gas sands, 5 oil sands, and numerous water sands in thernfive wells. The results of this assessment are shown via logrnexamples over specific intervals. In addition, several cross-plotsrncomparing open-hole data to cased-holed data show thernresults of this evaluation. Graphs of net pay, net effectivernporosity, net shale volume, and water saturation are shown forrnthe entire project.