Time-Lapse Feasibility Studies of Two Fields in the Niger Delta

Abstract

Time-lapse Feasibility Studies were carried out for two producing fields in the Niger Delta to assess the probabilities of success of acquiring 4D surveys. The two fields are located within onshore Niger Delta. Agbada field is located on land 100km North West of Port Harcourt, Nigeria. The field was discovered in 1960 and has been producing since 1965. To date some 66 wells have been drilled in the field. It has a STOIIP of about 1.5 billion barrels. Current estimate of undeveloped hydrocarbon reserves stand at Expectation Volume of 285 MMbbl and 0.8 Tscf. However, the field is experiencing high water cut and declining production. Agbada Field is covered by several vintages of 2D lines and one vintage of higher quality 3D seismic data that was acquired in the 1993. Kolo Creek field is located within the swamp, 110km South West of Port Harcourt, Nigeria. The field was discovered in 1961 but started production in 1973. It has a STOIIP of 495 MMSTB and an FGIIP of 1.3 TCF. Total Oil production to date is 254MMstb representing 45% of the STOIIP; and there has been no gas production. This field is also experiencing declining production and high water cut. It is also covered by several vintages of 2D lines and one vintage of higher quality 3D seismic data that was acquired in 1997. For each of these fields, it was desired to determine whether time-lapse signals will be detectable and to ascertain the optimum time in which to carry out a time-lapse monitor survey. The history matched dynamic simulation models for each field were converted to acoustic properties through a suitable rock model, and resultant acoustic impedances were calculated. Synthetic seismograms were subsequently generated for several time steps and analyzed for production-induced 4D signals. The impact of various levels of random noise on the 4D response was also evaluated. The results from both of these studies demonstrated that, even in the presence of significant random noise, production induced 4D changes should be observable if the monitor seismic survey is acquired in or beyond 2006. These results will be discussed.

Time-Lapse Seismic Monitoring of Onshore Reservoirs in Niger Delta, Field ‘K’ as a Case Study

“…If seismic is acquired over the same location with a time lapse, changes in amplitudes can therefore be evaluated (e.g. Osayande and Ugborugbo, 2009). Time-lapse seismic technology provides an aerial view of what is happening in the sub-surface using a volume of time shifts, the monitor volume can be aligned with the base volume to produce a time aligned monitor, which can then be used to calculate an aligned difference volume.…”