SAGD Well Pair Spacing Evaluation with Consideration of Central Processing Facility Constraints

Abstract

When developing properties using the steam assisted gravity drainage (SAGD) process, the lateral spacing between horizontal well pair spacing is extensively evaluated during well pad design to optimize resource recovery and economics. However, constraints associated with central processing facilities (CPF) are often not incorporated into the evaluation. With constrained steam supply and fluid processing capacity, the accelerated production that should accompany a reduced well pair spacing scenario may not be realized. In this paper, the economics of developing a SAGD property using 50m, 85m, 100m and 125m well pair spacing are compared within Suncor's MacKay River property. A production development planning tool is used to tie the individual well production profiles to a constrained CPF. While higher oil production rates, a cumulative steam-oil ratio (CSOR) reduction, and slight increase in oil recovery are observed at the well pad level in the 50m well pair spacing scenario, no accelerated oil production is achieved at the CPF level as steam supply and fluid processing capacities are constrained. With larger well pair spacing, the addition of more new pads on an accelerated schedule serves to maximize the CPF capacity utilization and oil production. Hence, the overall oil production at the CPF level is practically the same regardless of well pair spacing. With the areas evaluated in this study, the economics of the 85m, 100m and 125m cases are very close, with the optimum achieved at 100m well pair spacing. The 50m well pair spacing scenario produces the worst economic result as the tighter spacing case requires incremental capital for additional wells to achieve the same resource recovery. Without the accelerated production at the CPF level due to facility constraints or appreciable incremental oil recovery and CSOR reduction overall, there is no increased revenue to offset the increased capital outlay.

Integrated Economic Model for Evaluation and Optimization of Cyclic-Steam-Stimulation Projects

“…Typically, wells are brought online until steam-and/or emulsionhandling capacity is fully used. Various CPF constraints in IPM work flows have been discussed by Czwienzek et al (2009), Rodriguez Vera et al (2007, Cheung (2013), and Gu et al (2013).…”

“…Joshi et al (1998), Rodriguez Vera et al (2007, and Czwienzek et al (2009) present economic models applied to thermal heavy-oil projects in detail.…”

“…Stochastic simulation is implemented by means of a Monte Carlo model, by use of distributions assigned to input variables such as reservoir properties, capital costs, and prices. This type of model was defined by Czwienzek et al (2009) as a FISAM. A FISAM allows for the generation of a distribution of results, rather than only a single deterministic result.…”

“…A Monte Carlo model is only as worthwhile for analysis as the level of effort put into understanding and modeling its input-variable distributions. Studies by Czwienzek et al (2009), Rodriguez Vera et al (2007, Joshi et al (1998), Revana and Erdogan (2007), and Williams-Kovacs and Clarkson (2011) further discuss Monte Carlo methods for oil and gas applications. This study does not attempt to define the correct properties of the distribution for every input variable to a thermal heavy-oil model, but instead to demonstrate the novel work flow that was developed; that is, that Monte Carlo simulation can be applied to thermal heavy-oil projects by use of an analytical model.…”

“…One approach to modeling a thermal heavy-oil project involves an iterative work flow by use of models developed for the subsurface, surface, and economics aspects of the project. These types of models were referred to as IPMs by Czwienzek et al (2009), and this notation has been used herein. Fig.…”