Real-time data acquisition and interpretation needed for optimal offshore testing

Zhambyl Petroleum is licensed to explore an ultrashallow oilfield block offshore Kazakhstan in an area of extreme environmental sensitivity. This required Zhambyl to build a new barge drilling unit to access the field.

The operator chose Schlumberger to perform its first downhole test on its first exploration well, ZB-1, in the Zhambyl field. The main test objective was proving production capacity by obtaining representative samples of reservoir fluid. Considering the rig costs, Zhambyl required that data be immediately processed onshore concurrently with offshore operations.

Global support and expert collaboration deployed as solution

Schlumberger proposed transmitting real-time data using the InterACT global connectivity, collaboration, and information service to facilitate data monitoring and delivery from the well site to the Zhambyl office in Atyrau, Kazakhstan. All streaming data were visualized as time-scaled plots and as process-flow diagram panels, including alarm threshold settings. This expedited data access and quality control and helped onshore Zhambyl personnel to collaborate effectively with offshore crews and make informed decisions.

Next, Schlumberger suggested using RT Certain real-time test collaboration with reservoir experts, a service that enables data transmission as well as provides reservoir engineering support. Through this collaborative approach, Zhambyl petroleum optimized the well testing sequence by predicting reservoir and well behavior to ensure interpretable data for reservoir characterization. By working in a collaborative real-time virtual environment, the customer was able to evaluate and modify the well test program with certainty to optimize the data provided from each stage of the test.

The main priority during well cleanup was validating the unloading time of the well to ensure its effectiveness in saving rig costs. This involved Zhambyl monitoring the cumulative volume of retrieved cushion to predict the unloading time and bottomhole pressure, data which was then used to select choke size to control the time and underbalance within the formation and to prevent sand production. At the end of cleanup, the optimal main-flow choke size was determined to help give stable, single-phase flow within the reservoir as well as to improve pressure transient interpretation.

During the sampling flow period, the challenge was obtaining representative downhole PVT samples under stable flow conditions. Zhambyl requested using SCAR inline independent reservoir fluid sampling because it gives eight individually compensated samples, providing the greatest chance of obtaining high-quality samples from the downhole test string with no intervention required to sample.

Bottomhole pressure was calculated on the basis of wellhead pressure, flow rate, and vertical flow performance. Pressure data was also monitored to make sure fluid was in single phase at sampling point. Collaborative use of software enabled quickly calculating bottomhole pressures and inflow performance relationships for different sets of correlations as well as continuously monitoring the entire flow period.

Characterization decisions improved with no down time

Zhambyl acquired high-quality data for pressure transient interpretation and representative singlephase fluid for PVT analysis with zero NPT. By using InterACT service along with RT Certain collaboration, Zhambyl was able to efficiently meet its test objectives and optimize its upcoming campaign the following year.