Risk Evaluation for Production-Injection Recompletion and Sidetrack

Abstract

Using a decision tree and stochastic parameters, expected monetary value is calculated to evaluate optimal sidetrack time. In view of placing a high confidence level on analytical approach to optimal sidetrack time for a waterflooded reservoir based on possible uncertainty of economic and reservoir parameters and probability of sidetrack success, a major assumption on a parameter in a previous study is re-evaluated. Material balance and displacement efficiency are used to re-evaluate this critical waterflood performance parameter. The change in the relative influence of the stochastic parameters to optimal sidetrack time due to re-evaluation calls for much attention with probable need to further reduce assumptions made, however insignificant the parameter may be. This change will affect the degree of acceptability of the analytical approach. The probability of success of sidetrack sums up the geological and technical uncertainties, deconvolution of these will give the analytical approach an edge.

Sidetrack/Recompletion Time Evaluation by Proxy Model

“…Orodu and Tang and Lerche and Mudford [2,4] had in the past evaluated optimal sidetrack time under risk to exploit a less productive horizon with the continued production scenerio of the highly productive horizon under production. Orodu and Tang studied secondary recovery mechanism under water flooding while Lerch and Mudford did primary recovery.…”

“…Earlier studies have used analytical techniques to estimate production by exponential decline with uncertainty of success of sidetrack operation through probability of success and optimization of expected monetary value (EMV) to obtain optimal sidetrack time based on the schematic of Figures 1 and 2 [2]. Orodu et al and Orodu and Tang [3,4] previously, extended the application of obtaining optimal sidetrack time to a pair of production and injection well scenario and uncertainty of analytical production prediction parameters (see Figures 1b and 2 showing either simultaneous or sequential sidetrack from both production and injection wells). This study employs a proxy model to estimate net present value (NPV) and EMV to the study of [2] as a function of time of sidetrack/recompletion and basic reservoir parameters.…”