New Generation Sampling and Deep Transient Testing (DTT) Proves Significant Presence of Oil in the Partitioned Zone

Abstract A recent exploration well in the northern Partitioned Zone marked a significant milestone after a long pause in drilling activities. Reservoir characterization, focusing on factors like permeability-thickness, skin factor, reservoir boundaries, production potential, and fluid properties, is crucial for assessing reservoir behavior and optimizing production. The well showed high stratigraphic complexity, ranging from tight formations to high permeability zones. Alongside standard and advanced OH wireline logging, new-generation sampling and Deep Transient Testing (DTT) were deployed to understand the above factors. The success of the job demonstrated the value of deploying this new technology for the first time. This abstract highlight the challenges, achievements, and results of the first Sampling-DTT job. The multi-disciplinary team began planning months ahead to implement the logging program and ensure the necessary equipment was available. While the risk of differential sticking with sampling tools is high due to prolonged pumping, new generation technology has made dynamic well control possible using mud circulation to mitigate this risk. The toolstring featured an innovative focused radial probe with dual flowlines and powerful pumps, reducing sampling and DTT time. This advanced design improved data acquisition efficiency, enabling faster, more precise reservoir evaluations. The multidisciplinary team monitored the job 24/7 for timely decision-making. Five sampling stations, from Cretaceous reservoirs with one DTT station, were selected based on OH logs and pressure points data. The mobilities range for the stations were ranging from 0.1 mD – 100 mD respectively. All stations showed confidently 100% oil as mobile fluid. The average pumping time in high permeability stations was approximately only 1.5 – 2 hrs and that in tight formation was 3-4 hrs. This was smoothly achievable with high performance pumps in the string. The results were remarkable as well, DTT was able to reach till around 1000 ft inside the reservoir without observing any boundaries and revealing high permeability (Darcy rock) that is laterally extended showing good potential for further development. Also, strong pressure support is observed probably from the water aquifer below the oil zone. The approach of conducting sampling-DTT in exploration well has helped to achieve future cost savings by derisking of reserves uncertainty, determining zonal deliverability and it provides an alternative solution to conventional DST. Deep Transient Testing (DTT) is an advanced wireline technique that explores higher permeability and thicker reservoir zones with a larger radius of investigation, flowing faster and longer with high-resolution packages, compared to traditional Interval Pressure Transient Testing (IPTT). DTT is not a replacement for Drill Stem Testing (DST), rather bridges the gap between IPTT and DST, especially in multi-reservoir fields where testing all zones is costly. Additionally, DTT supports efforts to reduce carbon dioxide emissions.