Application of Coiled Tubing Fracturing Method Improves Field Production

Abstract

Abstract Application of a new coiled tubing assisted fracturing method (CTFM) has been implemented in the Elm Grove Field in Bossier Parish, Louisiana. The new method has allowed all potential pay intervals to be efficiently stimulated. As compared with traditional methods of stimulation, the new method has resulted in better sustained production. Introduction In an effort to effectively, efficiently, and affordably stimulate wells located in the Elm Grove Field in Bossier Parish, Louisiana, KCS Energy teamed with Halliburton in February 2005 to implement a new CTFM. The Hosston Formation was a known reservoir, but the geology of the field made it difficult to effectively stimulate all potential pay intervals. Until February 2005, KCS Energy had been stimulating the Hosston Formation using traditional methods of plug, perforate, treat, and repeat. KCS Energy was attempting to treat well sections of several hundred feet with one large high-rate treatment. The large well sections contained small pay intervals separated by laminated nonpay intervals. Traditional methods of stimulating large well sections frequently result in two prominent issues:1,2there is no way to ensure that all pay intervals are stimulated because of the variations of fracture gradients and issues of limited entry, and it is expensive to isolate each pay interval using a bridge plug and perforation run;the Hosston Formation is highly laminated. The majority of pay intervals are four to eight feet thick and separated by water saturated layers. This lamination of the pay intervals makes it difficult to effectively stimulate the formation. The solution to these issues is a new CTFM. Several papers have been written on this process.3–7 The CTFM consists of performing hydrajetting operations down a coiled tubing (CT) string. Upon completion of the hydrajetting operation, the stimulation is performed down the annulus. The final stage of the stimulation contains a heavy sand concentration in a low-viscosity fluid that is used to isolate the stimulated zone from treatments farther up the wellbore. After the slug settles, the hydrajetting operation is performed in the next target zone and the entire process is repeated, making it possible to treat all potential pay zones during one CT trip out of the wellbore. General Discussion The Hosston Formation in the Elm Grove Field is located at depths ranging from 5,500-8,000 feet. The porosity of the formation ranges from 8-10%. The formation is normally pressured and water saturation ranges from 15-95%. Traditional stimulations yield high initial gas production but have a sharp decline. Water production is high, ranging from 50-300 BWPD. Traditional treatments of the Hosston Formation consist of pumping 500,000-1,000,000 lb of 20/40-mesh proppant at rates ranging from 50-75 bbl/min across intervals ranging from 100-300 ft in height. The 100- to 300-ft well section contains multiple perforation intervals of 2-10 ft in height. This type of treatment is inefficient because entry is limited and noncontributing intervals of the wellbore are exposed to excessive amounts of proppant and fluid. Treating these large intervals with one blanket treatment exposes the formation to unnecessary volumes of damaging treatment fluids. Additionally, sand is placed in noncontributing intervals or largely water-saturated intervals. Implementation of the CTFM made it possible to remove these problems from the stimulation design and placement. Individually perforating and stimulating each pay interval made it possible to tailor each treatment, instead of using a blanket treatment to stimulate all of the intervals at once. Case History of Well A---Elm Grove Field, Hosston Formation, Bossier Parish, Louisiana Well A (see Fig. 1) was traditionally stimulated on June 10, 2004. The Hosston Formation was isolated. The stimulation consisted of approximately 500,000 lb of 20/40-mesh proppant with an average treating rate of 53 bbl/min. The well contained five perforation intervals, as shown in Fig. 1. The intent of the job design was to stimulate a 390-ft interval with one large treatment at a high rate. Tracers of scandium, antimony, and iridium were run during the treatment to determine where the majority of the treatment fluid was placed. Upon evaluation of the tracer survey (Fig. 2), engineers determined that the entire interval had not been treated.