Simulation of Horizontal Wells For Winter Cummings Sand Pool
Authors: Ko S.C.M. , Bohun D. 
Published: March 2010

Abstract
To determine the optimum spacing for the development of heavy-oil-over-water reservoirs by an array of horizontal wells, a quick and inexpensive but rigorous two-dimensional (2-D) cross-section simulation model containing 340 cells in an element of symmetry was developed. Its validity was tested against a 4,760 cell three-dimensional (3-D) model. The 2-D model was calibrated by history matching a horizontal well with 17,000 m3 of fluid production. At the low flow rates typical in heavy oil applications (governed by wellbore inflow performance, lifting system capacity and sand control considerations), the pressure drop along the horizontal wellbore from "toe" to "heal" is insignificant, rendering acceptable accuracy from the 2-D model.
The fine grid system in the 2-D- model also permitted the analysis of the development of the water crest with time. Additionally, the effects of reservoir stratification, standoff from the water-oil contact, production rate, oil viscosity, relative permeabilities and degree of pressure support from the aquifer were investigated. Based on-the study results, optimum interwell spacing was determined for the Winter Cummings Sand Pool.
Although this model was applied to a particular reservoir, it is app1icable to any oil-over-water reservoir producing at relatively low rates, for spacing determination and performance prediction.

Introduction
The Winter Cummings Sand Pool is located in Townships 42 and 43, Range 25, West of the Third Meridian, which is about 100 kilometers southeast of L1oydminster, as shown in Figure 1. The pool was discovered in 1979 by the drilling of well 13-27-42-25W3 which encountered an 18 m oil column over 10 m of water (Figure 2). An encouraging initial production rate of up to 6 m3 per day from well 13-27 led to further drilling until early 1983. When the 14th well, 16-29, which was drilled in virtually the centre of the field, encountered no oil column at all, further field development was suspended and a geological review was initiated. This, together with the introduction of the National Energy Policy, ended further development with 13 producers and one cased potential service well in place (Figure 3).
After 1983, the wells were produced at rates of about 4 to 5 m3 of oil per day before water breakthrough, which occurred after 300 to 3,000 m3 of oil production. With the oil price collapse in 1986, the entire pool was shut-in due to poor economics. At this time, cumulative oil production was only 23,000 m3 or 0.02% of the original oil-in-place.
FIGURE 1: Location of Winter Pool. (Available in full paper)

Horizontal Well Pilot - Phases I and II
Although the horizontal well alternative was considered as early as 1984, the high capital investment, in combination with the technical uncertainty at the time, led to a prolonged period of evaluations, re-evaluations and negotiations culminating in a farm-out agreement involving a pilot consisting of a minimum of two and a maximum of five horizontal wells, over a two-year period. The first phase of the pilot involved two wells (A6-32 and B14-28-42-25W3M) and the second phase involved three wells (B7-29, A2-33 and A7-32-42-25W3M).