Micro-Emulsion Effectiveness for Twenty Four Wells, Eastern Green River, Wyoming

Abstract

Abstract The evaluation of 24 wells representing 339 stages of fracture stimulation which produce from the Lance interval in the northeastern Pinedale Anticline area of the Green River Basin, Wyoming has been conducted to determine if the use of a micro-emulsion (ME) surfactant intended to reduce permeability impairment and improve load recovery, had any observable benefits. The well group consisted of wells in a limited contiguous six square mile area, with 10 wells having 1.5 gallons of ME per thousand used throughout the fracture stimulations, but at no other time during in-well operations. Fourteen wells completed approximately nine months earlier had no micro-emulsion used during stimulation or other in-well operations. Based on the matched reservoir properties and effective degree of stimulation, 20 year forecasts were performed for each well. Then comparisons of those results and various treating parameters were used to assess the potential benefit arising from using ME. The determination of potential benefit was assessed using classical statistical methods to ensure that the interpretation was as unbiased as possible. From that analysis, there is distinct and clear benefit from using the micro-emulsion to facilitate placing the fracture stimulations, to increase effective fracture length, to minimize damage arising from operational shut-ins and especially to increase gas recovery and net present value of wells in which the micro-emulsion system is used. Review of Prior Work Three papers of particular interest have been written regarding performance assessment of different completion, stimulation and materials selection. Pursley, Benton, Nordlander, etal. (1) examined six low permeability gas wells in West Texas, concluding that the wells in which a Micro-Emulsion (ME) was used a) had better reservoir conductivity, b) longer effective fracture lengths, c) better resistance to damage resulting from shut-in events and d) better long-term performance than those without it. Two of the papers deal specifically with the Pinedale Anticline area of the Green River Basin, Wyoming. Eberhard and Mullen (3) investigated the effectiveness of different methods of zone isolation during multi-stage fracturing operations in Jonah Field at the south end of the Pinedale Anticline. Their performance metric was the cumulative gas production for either a six or twelve month period, in conjunction with a variation of the classic moving-domain procedure (4). They made no attempt to evaluate individual stage performance or do any reservoir characterization to assess those effects on their conclusions. An evaluation of the effectiveness of various proppants was conducted by Vincent, Huckabee and Conway (5). They evaluated 30 wells representing 446 fracturing stages in four different areas of the Pinedale Anticline. This paper employed limited statistical analysis methods to each stage by assigning a reservoir quality (log derived permeability * thickness), simulated fracture conductivity and a production rate for each stage derived from one or more production surveys at approximately 100 days production following stimulation. The paper states that using "decline curve analysis" is a non-unique method to determine reservoir and fracture properties. Based on the graphs they show, the methodology was not properly applied, nor was the production data suitable for the purpose.