Abstract

Foams have been used as hydraulic fracturing fluids for over twenty years. Their primary usage is in reservoirs that are under-pressured and/or water sensitive. Nitrogen was the gas initially used as the internal phase. Later, carbon dioxide became sore widely accepted and provided better load recovery and production.

Now, a third generation of foams has been developed. Nitrogen and carbon dioxide used simultaneously as the internal phase has shown to further improve load recovery and production rates.

This paper will present a brief review of foam fracturing procedures and mathematics. monitoring hardware and software requirements, rigging up and safety requirements. The majority of the paper will canter on foam fracturing treatments performed on low permeability reservoirs in Northwestern Oklahoma. A comparison of past and present treatments and production rates utilizing operator supplied logs and production data will be presented. overall, the new Binary Foam treatments presented. overall, the new Binary Foam treatments have shown to be beneficial from a treatment application viewpoint. Advantages include (reduced screenouts), increased load water recovery, decreased flaring time due to lack of pipeline acceptable gas and improved production pipeline acceptable gas and improved production rates.

Introduction

This field study is a comparison of fracture stimulation treatments of tight gas sandstones in the Northwestern shelf of the Anadarko Basin of Oklahoma (Fig. 1). The Morrowan and Virgilian (Tonkawa) sands are prolific gas producers. The study area consist of prolific gas producers. The study area consist of Beaver, Ellis, Harper and Woodward counties.

Approximately 50 wells were utilized to evaluate the effectiveness of stimulation treatments performed on the sandstones. Two localized fields performed on the sandstones. Two localized fields (1 and 2 - Table III) exhibited the characteristic pattern of the study. Well logs and production pattern of the study. Well logs and production data were provided by the operators experienced in the area. Original stimulation treatments in the 1960's consisted of 10,000 to 100,000 gallons of water pumped at rates of 8 to 25 barrels per minute in pumped at rates of 8 to 25 barrels per minute in order to place walnut shells as proppant. Amazingly, these stimulation treatments did enhance production of the wells, in some cases from 150 production of the wells, in some cases from 150 mcfpd to 3500 mcfpd. These treatments were the basis of the cliche "You can't screw up a good well". The sands were over-pressured at the time of theme treatments. conversely, present day reservoirs are normally under-pressured by as much as 50 percent of their original pressures (Table 1). Today the consequences of pumping the wrong fluid in a well is devastating and can cause the loss of a well. Productivity increases surpassing the 1960's Productivity increases surpassing the 1960's stimulation treatment results can be achieved today even with the decreased bottom hole pressures. These results can be accomplished with quality job execution and by using proven treatment and stimulation fluids.

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