Well testing generates essential reservoir data, and although it can impact initial operating expenditures significantly in oil or gas upstream projects, the data generated can be essential to the efficiency of the completion operation ultimately designed. While having proven its value, data-gathering methods still must be balanced with operational and economic strategies, if the completion goals are to be economically feasible. Drill-Stem Test (DST) tools with downhole shut in and memory gauges are commonly used in well testing operations to provide reliable data and enhance operational efficiency of the completion. However, DST tools alone cannot monitor reservoir pressure response in real-time for justifying the subsequent operational objective changes during the data acquisition, because the recorded data cannot be retrieved at surface until the well test operation is completed, and the workstring is pulled out of hole. To overcome this problem, surface read-out (SRO) systems can be used with DST for retrieving downhole memory-gauge data in real time; thus, the pressure response can be monitored directly, and operational changes can be made immediately, based on actual reservoir conditions. An SRO system was used in Senoro-6 well to aid in justifying a shut-in duration to reach reservoir boundary and attain information that indicated the need for a stimulation treatment. Based on the real-time SRO data, it was found out that the permeability was lower than expected, and shut-in should be terminated earlier than planned, since the required shut-in time to reach boundary would be much longer than anticipated. Prolonging testing time would not be reasonable when reviewing operational and economic considerations. In addition, pressure transient analysis from real time SRO data indicated that the well had severe wellbore damage. Thus, the decision was made to conduct matrix acid stimulation based on the SRO data and to continue with post-stimulation well testing without pulling the DST string out of the hole. Post-test results showed a 22% production improvement, while the operation itself saved more than US$150,000 from daily rig cost. This approach in using the SRO system proved to be effective in helping to determine an efficient testing operation and completion strategy.

A brown field, offshore Sarawak, Malaysia, with multiple sub-layered laminated sands of varied pressure regimes and mobility ranges, was challenged by depletion, low mobility and uncertainty in the current fluid types and contacts. Optimal dynamic fluid characterization and testing techniques comprising both Wireline and Logging While Drilling (LWD) were applied in nine development wells to acquire reliable formation pressure data and collect representative fluid samples including fluid scanning. Some of the latest technologies were deployed during the dual crises of falling oil price and the Covid-19 pandemic. The S-profile wells were drilled using oil-base mud (OBM) with an average deviation of 60 degrees. Formation Pressure While Drilling (FPWD), Fluid Sampling While Drilling (FSWD) and wireline formation testing, and sampling were all utilized allowing appropriate assessment of zones of interest. Various probe types such as Conventional Circular, Reinforced Circular, Elongated, Extra-Elongated and Extended Range Focused were used successfully, ensuring that the right technology was deployed for the right job. Formation pressure and fluid samples were secured in a timely manner to minimize reservoir damage and optimize rig time without jeopardizing the data quality. As a classified crisis due to the pandemic, rather than delaying the operations, a Remote Operations Monitoring and Control Center was set-up in town to aid the limited crew at rig site. A high success rate was achieved in acquiring the latest formation pressure regimes, fluid gradients, scanning and sampling, allowing the best completion strategy to be implemented. With the selection of the appropriate probe type at individual sands, 336 pressure tests were conducted, 44 fluid gradients were established, 27 fluid identification (fluid-id / scanning) pump-outs were performed, and 20 representative formation fluid samples (oil, gas, water) were collected. Amongst the Layer-III, Layer-II and Layer-I sands, Layer-I was tight, with mobility < 1.0 mD/cP. Wireline focused probe sampling provided clean oil samples with 1.4 to-3.7 wt. % OBM filtrate contamination. The water samples collected from Layer-II during FSWD proved to be formation water and not injection water. The wells were thus completed as oil producers. Reliable fluid typing and PVT quality sampling at discrete depths saved rig time and eliminated the requirement of additional runs or services including Drill Stem Testing (DST). This case study has many firsts. It is the first time where latest fluid characterization and testing technologies in both Wireline and LWD were deployed for an alliance project in Malaysia and that too during dual crises of falling oil price and the pandemic aftermath. Overcoming various challenges including limited rig site manpower, there was no delay in completing the highly deviated wells with tight formations in a single drilling campaign and provided rig time savings. For the purpose of this case study, two wells have been discussed. First well used the wireline focused sampling technology and the second used the FSWD technology.