The purpose of this work is to develop a new method suitable for hand calculation. Simulation is shown to be a cumbersome process to investigate and predict optimum oil rate based on maximizing economic recovery, and breakthrough time for both vertical and horizontal wells. Since the early days, several experiments and mathematical analyses were conducted to solve coning problems, since the production of water and gas increase the cost of producing operations, reduce the efficiency of the depletion mechanism, and the overall recovery. One of the basic conclusions of many analyses was if oil is produced at a sufficiently low rate, coning of water and gas can be avoided, and only oil is produced. This low rate is called critical oil rate.
These different theoretical correlations are conflicting and give different answers, probably due to the different assumptions each of them involves, and many times the critical rates are too low, and for economic reasons, a well is frequently produced in field operations at a rate above critical rate. This results in production of water, gas as well as oil, which could results in a low economic recovery.
To overcome this problem, an extensive parametric sensitivity analysis of the various reservoir and fluid properties on water and gas coning was investigated and performed using numerical simulation to provide input data for developing a new predictive correlation needed to calculate breakthrough time and optimum oil rate based on maximizing economic recovery for both vertical and horizontal wells. The parameters were grouped based on the regression analysis.
The new method is more robust, where the developed empirical correlations were tested and found to be reliable and closely accurate in estimating optimum oil rate to be used for a well in field operations. These correlations are illustrated with several field examples from Hassi R'mel field, Algeria, where calculated and observed, show satisfactory agreement of correlations with production data.
Determination of appropriate oil rate for maximum economic oil recovery is a complicated and controversial issue in oil field development. The reservoir of Hassi R'mel oil rim, Algeria, contains thin oil columns of 30 feet average overlain by a huge gas cap with a bottom aquifer support. Recovery of the oil is difficult because water and gas coning results in low oil production rates. Water and gas coning are serious problems in many oil field applications, where the production of water and gas from a thin oil reservoir is a common occurrence, which increases the cost of producing operations, and reduces the efficiency of the depletion mechanism and the overall recovery. We will deal with one cause of this production namely, coning.
One of the main reasons for coning is pressure drawdown. A vertical well exhibits a large pressure drawdown near the wellbore, whereas horizontal well exhibits minimum pressure drawdown, thus horizontal wells provide option whereby pressure drawdown can be minimized, coning tendencies can be minimized, and high oil production rates can be achieved.
