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Abstract

Development of the Pinedale Anticline (PDA) of western Wyoming is proceeding at a rapid pace. During the past five years, approximately 500 million pounds of proppant have been placed into nearly 200 new wells. Despite this high activity level, no clear consensus has emerged from the various operators as to the optimal stimulation design. Proppant costs range from less than 20% to greater than 65% of the stimulation service company ticket dependent on proppant type selected. For one operator, proppant costs represent approximately 30% of the total completion cost and are a target for cost reduction efforts. These cost reduction efforts must be balanced with the economic value of proppant conductivity and its relationship with effective fracture half-length.

This paper summarizes results from a field trial that was implemented to investigate the effect of proppant selection upon productivity from low-permeability (0.0006 – 0.015 md) formations of the Pinedale Anticline.  This study compares the production from 452 fracture treatments in 30 new wells completed by Shell Rocky Mountain Production during the past three years. Production logs are used to compare the productivity of fractures propped with 20/40 sand, 20/40 resin-coated sand, 20/40 economy light-weight ceramic, broad- sieved intermediate strength, and 20/40 intermediate strength proppants. The results from this study are believed to be the first published field comparison of broadly-sieved and tightly-sieved ceramics.

This trial predominantly maintained a consistent stimulation strategy to reduce complexity and uncertainty in the analysis of the proppant selection evaluation. Proppant selection was varied by stage dependent on depth and geologic intervals to provide reliable offset comparisons. Results are categorized by geologic interval to reduce uncertainties from variations in reservoir quality and pressure differentials to more accurately assess the impact of altering proppant type. Economic analyses are presented to illustrate the most cost effective products to incorporate into each fracture treatment. Actual field results are compared to model predictions and laboratory results to determine whether proppant strength and sieve distribution affect production in a predictable manner.

Overview of the Pinedale Anticline

Gas-saturated Lance sandstones were discovered in the Pinedale area in 1939. Figure 1 illustrates the location of the Pinedale Anticline (PDA) in Western Wyoming in the United States of America. From 1950 through 1990 operators drilled more than 50 wells into the Lance along the Pinedale Anticline; 27 of those wells are producing today. Development activity is high, with 200 new wells completed by 10 operators during the last five years.