Optimum Well Type for Oil Rim Reservoirs with Large Gas-Cap and Strong Aquifer

Abstract

Oil rim reservoirs are often troublesome to produce commercially as a result of the adverse effect of coning and cusping/cresting. In this study, deviated and horizontal wells were employed to determine the optimal well type to be drilled in the "GISO" oil rim reservoir in order to attain optimum oil recovery while reducing uneccessary cost. The GISO oil rim reservoir considered in this study had a thickness of 8ft with grid dimensions of 91×74×20 in the i, j, and k coordinates respectively, and contained a dynamic reservoir oil volume of 9.37MMSTB. Results obtained from simulation revealed that there was not enough oil recovered from the subject oil rim reservoir, owing to the fact that that the reservoir had a very small oil column thickness and this led to the early encroachment of water into the oil column. Three horizontal wells and one deviated well were simulated in the oil rim in order to determine the preferred well type for optimum hydrocarbon recovery for a period of 20 years. The four cases were simulated with a constant production rate of 2000STB/D. Well H1, a horizontal well with lateral length of 272ft recovered 840MSTB, while well H4, a deviated well with a deviated well case with an inclination angle of 84.20° from the GOC and lateral length of 242ft recovered 830MSTB.

Optimizing productivity in oil rims: simulation studies on horizontal well placement under simultaneous oil and gas production

“…In their summary of the effect of well placement on thin oil rims with bottom and edge water drive, Kabir et al (2004) analyzed that well placement relative to fluid contact among other less essential factors is essential to optimizing oil recovery. Optimizing horizontal well placement in oil rim reservoirs is essential to oil recovery as noted by Ogiriki et al (2018), Carpenter (2015) and Keng et al (2014). Much of their work focused on a single type of oil rim reservoir, use of few important parameters that affect productivity, focus on horizontal well length and neglect of parameters such as height of oil rim, sizes the gas caps and aquifers.…”

Mathematical Approach to Determination of Optimum Oil Production Rate in Oil Rim Reservoirs

“…The threat of producing oil rim reservoirs comes from the strategic location of the oil in relation to the other reservoir fluids which pose serious operational and economic challenges using existing conventional methods of optimizing reservoir development. The presence of a wide range of uncertainty, the peculiar complexity in the distribution of the resident fluids and geological strata geometry, have made efficient development and production of thin oil column a difficult task [4,5].…”