Waterflood History Match Study of the Torchlight Tensleep Micellar Pilot
Authors: Grantz Robert E. 
Published: December 2007

An isolated five-spot pattern was installed in the shut-in, previously waterflooded Tensleep formation of Torchlight field. The ultimate purpose of the pilot is to test micellar/polymer flooding. The pilot has produced significant secondary oil under pilot produced significant secondary oil under pilot preflush operations. A two-dimensional, two-phase preflush operations. A two-dimensional, two-phase black-oil reservoir simulator was used to develop a reservoir description that gives a match of pilot preflush waterflood operations. preflush waterflood operations.

Introduction

The Torchlight field is in the Big Horn basin of Wyoming. Fig. 1 shows its location in relation to other production in the area. Amoco Production Co. plans to perform a micellar pilot test in the Tensleep plans to perform a micellar pilot test in the Tensleep formation. The design and interpretation of the pilot require a detailed reservoir description of the pilot area. A key factor for pilot interpretation is the oil saturation before micellar injection. This paper describes a two-layer geologic reservoir description that was developed to match pilot preflush waterflood performance. The developed reservoir description will give the water saturation distribution at the time of micellar injection.Previous Amoco petrophysical work on the Torchlight Tensleep field identified the presence of a correlative anhydrite layer in the vicinity of the pilot and at Well 54, the pilot producer. The anhydrite layer effectively separated the reservoir into two distinct, noncommunicating geologic layers in the vicinity of the micellar pilot area. The upper layer is not present throughout the entire field. This geologic interpretation was a key factor in obtaining the final performance match. Once the geologic description performance match. Once the geologic description was built into the reservoir simulator, the approximate correct performance was obtained easily. The five key parameters in the reservoir description are (1) areal extent of the upper layer, (2) porosity, permeability, and thickness contained in each layer, permeability, and thickness contained in each layer, (3) aquifer strength of the two layers, (4) areal water saturation distribution in each layer, and (5) effect on individual layer productivity at the wellbore of a workover on the pilot producer. The final match and the sensitivity of each of these parameters on the match are discussed in this paper.

Model Description

A two-dimensional, two-phase black-oil model was used to simulate the pilot performance. The modeled area is shown in Fig. 2. Also shown is the pilot location in relation to Tensleep productive limit. A 32 x 31 grid system covered the entire Tensleep reservoir. The limited water drive of the Tensleep reservoir was modeled by use of an artificially high porosity value in the outer row of grid blocks to porosity value in the outer row of grid blocks to simulate aquifer pore volume.Two distinct geologic layers were simulated in the model. The two-layer description was a key item in obtaining the performance match. The layering is discussed later.The model was controlled by producing oil rates and water injection rates. The control rates were volumetric monthly averages to ensure that correct total volumes of fluid were injected and produced. The desired result of the model study was a match of WOR and bottomhole pressure (BHP) on the producers and a match of injection pressure on the producers and a match of injection pressure on the pilot injectors. pilot injectors. Quality reservoir data for input into the model were available.

JPT

P. 1599