Topic: Logging-While-Drilling (LWD) Pressure Data Acquisition, Interpretation & Challenges: A Case Study from Offshore Niger Delta
The Lagos May Technical Meeting was held on May 17, 2017 at the Grand Ballroom of Eko Hotel and Suites, Victoria Island, Lagos. The technical presentation was made by Akomeno Oyegwa, an Earth Scientist with Chevron Nigeria Limited. The topic presented was "Logging-While-Drilling (LWD) pressure data acquisition, interpretation and challenges: A case study from Offshore Niger Delta - Okan field example. In the case study, an LWD tool was used to acquire pressure data in three recently drilled wells within a chevron mature field located offshore Niger Delta. The field has been on production for over 50 years. Although considered a brown asset, the field still has great production potentials from possible by-passed pays and thin undeveloped reservoirs. The core objectives of the data acquisition campaign were to measure depletion, determine fluid densities, establish fluid contacts and to check for reservoir compartmentalization. The current acquisition and interpretation results presented some challenges and interesting information that queries previous assumptions on the field, e.g the ability to adequately interpret fluid types and contacts from conventional log signatures even in seemingly clean reservoir intervals. In one of the wells, resistivity log suggested hydrocarbon water contact position, porosity logs suggested hydrocarbon beyond/below the limits suggested by the resistivity while pressure profiles confirmed the fluid type as oil and fluid contact as correctly described by the resistivity log. In a second scenario, there was a case where pressure data helped to differentiate two unconnected reservoirs having a pressure difference of 11psi. Pressure data must be integrated with other logs as there could be discrepancies or wrong predictions from pressure data tool. The key lesson learnt from the acquisition and interpretation process is that basic log data are not always conclusive/sufficient to determine reservoir fluid type and contacts, especially in mature fields. The recommendation was that pressure data should be integrated with other logs and acquired while drilling using LWD to avoid re-entry and refill. Downhole fluid analysis/sampling should be considered especially in fluid typing and it is required that the mud pumps should be working perfectly well in order to effectively manage and reduce the duration for pressure data acquisition.
The meeting was sponsored by Chevron Nigeria Limited.
For the Presentation, Click Here.
For the Meeting Pictures, Click Here.