How to Obtain Reservoir Pressure and Fluid information in Low Permeability to Tight Reservoirs: Case Study from Malaysia
Formation evaluation of tight formations, of very low porosity and extremely low permeability, combined with heterogeneous reservoir properties and laminations is very challenging especially during the early life of the field. The key challenge is to evaluate the potential of these low-quality rock reservoirs while minimising development costs in the early development phase. With the increased challenges imposed by complex well trajectories and difficult hole conditions, traditional methods used to test the formation are no longer practical, or cost efficient. Conventional logging / testing techniques have been proved to be affected by various uncertainties which leads to inaccurate formation evaluation results. On the other side, conventional Wireline Formation Testing (WFT) technique using conventional probe has worked well in wide range of reservoirs, but it is not the best option to use when it comes to pressure and sampling measurements in tight formations. Therefore, a new testing technique is required to acquire valid formation measurements of the zones of interest to reduce reservoir uncertainties and allow better reservoir characterization. Recent advances in wireline formation testing has introduced 3D radial probe that make it possible to perform measurement in such challenging reservoirs. This paper presents two successful case studies from offshore Malaysia, in which complex reservoirs are tested for formation pressure measurement and downhole reservoir fluid characterization. In the first reservoir, the formation is extremely tight, and in the second reservoir, formation evaluation challenges are low mobility formation (< 10 mD/cp), and reservoir pressure is closed to the saturation pressure. Conclusive reservoir fluid identification is not clear from other openhole logs due to low resistivity play, and high quality single phase samples are required to prove reserve and select completion zones. This paper also discusses a careful job planning from (1) examining large field data base to plan for this particular job, (2) Simulated different probe/inlet and pump type for expected reservoir properties (3) Simulated time for different type of probes. This paper also integrates good operation practice to make sure that the best possible data can be achieved within the effective logging time.
AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018