Overview and Challenge

The East Tunstill Field is a tight, under-saturated sandstone reservoir with a 9% recovery factor on primary depletion. Marginal current production and a previous relatively unsuccessful waterflood did not present the potential value of the field. In order to present this value, within a limited budget, new procedures and methods were necessary. A project workflow was designed to handle the field characteristics of a high number of wells and many years of production, resulting in a large amount of data that could be used to achieve a better analysis.

The operator, Penn Virginia (“PVA”), believed an improved reservoir description applied with simulation methods could yield a better understanding of previous drainage, fluid movement, and the volume and location of the remaining oil. Additionally, the operator decided to utilize a new volumetric balancing technology that allowed a fast (15 minutes) analysis of various waterflood injection/producer patterns to derive the most economic and efficient flood pattern and thereby highlighting its potential.

Background

The East Tunstill Field is located in Loving County, Texas within the Delaware Basin. Discovered in 1959, cumulative production is estimated to be 2.9 MMBO, 8.2 BCF, and 5.8 MMBW. The field produces from the Delaware “Olds”, in the upper Bell Canyon sand series. The conceptual depositional model is depicted in Figure 1. An improved reservoir description study with reservoir parameters calculated Original Oil-In-Place (“OOIP”) to be 30 MMBO. 

Project Workflow and Methodology

A workflow was designed to achieve PVA’s goals. This workflow is a disciplined and orderly flow of tasks comprised of standard geologic and engineering functions. This methodology has been used successfully on older, mature fields where there are many wells and complex stratigraphy or facies.