Optimal development of deepwater slope system reservoirs in Block-14, Angola, requires proper determination of Original Oil in Place, reservoir connectivity, and lateral heterogeneity. The uncertainty on these parameters can be reduced significantly by using high frequency pressure and production data and pressure versus depth profiles acquired while drilling to augment and calibrate pre-existing interpretation from seismic, cores and logs. The Block-14 Tombua-Landana Drilling and Production Platform was built to develop 8 channelized reservoirs, which have different degrees of heterogeneity and net-to-gross ratios. This variability was recognized early during the development program and resulted in a wide range of initial production rates and declines. In response to this, producers were designed with permanent downhole gauges to improve reservoir surveillance capabilities for better determination of well count and optimal placement of producers and injectors. In addition, real time data integration tools were implemented to facilitate performing real-time dynamic modeling.
Once started operating, downhole and wellhead well-data are transmitted and stored in a data repository. This information is integrated with well-tests and used to calibrate reservoir-to-surface wellbore models and generate real-time production profiles. The workflows capture planned and unplanned shut-ins, are used to perform pressure-transient analysis and determine static pressure. By performing material balance and reservoir simulation modeling, we have been able to determine oil in place, quantify the degree of support from offset injectors, assess interwell connectivity, calibrate and update specific aspects of the geological model and optimize the development plan for each reservoir. These workflows also contributed to predicting well events such as scaling, sand production, and water breakthrough.
This paper describes examples of surveillance and dynamic modeling for wells in the Tombua-Landana (T-L) fields and describe how permanent downhole data has improved reservoir management.