The Value of Logging While Drilling (LWD) Pressure Data in Deepwater Tracts, Offshore Angola

Silva, Ilidio Domingos¹, Frederico Ferraz Domingos¹, Chris Freitag², Eduard Van Wijk², Arno Buysch² (1) Sonangol, Luanda, South Africa (2) Baker Hughes INTEQ, Houston, TX

Time efficient acquisition of formation evaluation data is of paramount importance in the deepwater and ultra-deepwater exploration and development wells in West Africa, where the total daily operating costs of drilling units can be well over 300 kUSD. With the recent intro­duction of a new Logging While Drilling tool, it is now possible to measure formation pres­sure while the well is still being drilled. This represents a significant time and cost savings opportunity, simultaneously improving drilling efficiency and safety while reducing risk and Non Productive Time (NPT).

An accurate and early knowledge of formation pressures in the drilling phase allows con­fident decisions to be taken with respect to selection of casing points, thereby enhancing the safety of the drilling operation. Formation pressure data can also reveal the connectivity of reservoirs, thereby allowing improvements in well placement or the completion strategy to be made in real time. Early formation pressure data in conjunction with other LWD data enables the operator and the governing authorities to reach timely decisions regarding aban­donment of wells.

Recent technological developments in an LWD formation pressure tester tool have made it possible to acquire formation pressure and mobility data in the drilling phase in the short­est possible time, typically in less than 5 minutes per set of pre-and repeat tests in the high­ly permeable deepwater sands in Angola. In high permeability zones time lapse data has pro­vided important information on the pressure draw- down caused by concurrent production in nearby wells. Comparison with pressure data from wireline formation testers has shown the accuracy of the data being recorded with the new LWD tool.