Solving Formation Evaluation Challenges Using a Combination of Open and Cased Hole Logging Technology

Abstract A combination of open and cased hole logging technique was used to carryout formation evaluation in a high angle well traversing laterally displaced reservoir complexes. This method was adopted to minimize wellbore exposure and avoid risks attending logging the high angle open hole. Hence, with limited open hole data, Quad (cased hole neutron technology with dual physics), noise and production logs were used to determine reservoir properties. The formation evaluation objectives were achieved using a combination of MLWD, mudlog and Quad neutron logs. After cementing the final hole section at 62deg, cement evaluation and Quad neutron logs were used to firm up perforation. Noise and Production logs were also acquired to assess perforations and estimate reservoir pressures and injectivity indices. Porosity, hydrocarbon saturation, clay volume and relative bulk density of the reservoir complexes were estimated from a set of logs obtained from the cased hole neutron technology which combines neutron-gamma and neutron-neutron physics. Fluid type and contacts were also independently determined and oil saturation across a 30ft reservoir interval with anomalous LWD-Resistivity response was resolved from these logs. Integration of cement evaluation logs with the Quad logs was useful in identifying channeling across one reservoir complex of interest. This helped to optimize initial perforation and completion designs. Two independent estimates of reservoir pressures were obtained from analysing Noise and Production logs. Perforation performance and productivity indices were determined from injectivity test analysis. This data acquisition strategy demonstrates innovative implementation of low risk and cost-effective resolution of data acquisition challenges in complicated situations are feasible. This paper is meant to demonstrate that improvements in cased hole technology has cost-effectively made derivation of quality petrophysical data achievable, in the absence of sufficient open hole data. It is also worth considering as an alternative to open hole data acquisition in complicated situations to mitigate associated risks.