Overcoming a Cementing Failure: Sequenced Fracturing Technique for Remedial Application

Abstract

The Cottage Grove formation is an active U.S. mid-continent play where cemented horizontal wells are traditionally stimulated by fracturing several perforation clusters simultaneously using limited entry "perf and plug" or other multi-stage completion solutions. Leaving sections of the lateral unstimulated when fracturing over a large interval can be even more severe in un-cemented completions, where the limited entry technique cannot be relied on to distribute the flow of stimulation fluids in the reservoir. Prior to the introduction of the sequenced fracturing technique, there was no solution to reliably stimulate a large un-cemented or openhole sections. This lead to potential losses of EUR in those wells where for some unplanned event, a section of the wellbore cannot be cemented or isolated with plugs. Recently, a well was drilled and unforeseen issues resulted in 3,300 feet of casing with a completely un-cemented annulus. A remedial cement job was not a feasible option and was quickly dismissed. It was decided to use a new sequenced fracturing technique to complete the stimulation without compromising EUR. This technique uses degradable fibers and multi-sized particles as a composite pill to temporarily plug the fractures and divert stimulation slurry to other regions along the wellbore. In this instance, 20 fracturing stages separated by 12 composite pills and 9 bridge plugs were pumped in sequence to optimize the number of fractures along the wellbore and maximize production.A production and radioactive tracer log run after the operation revealed that the composite pill successfully diverted the treatment fluids from areas previously fractured to previously unstimulated portions of the lateral. As a result, the entire lateral which had been left without cement was ultimately evenly stimulated. This was confirmed by a production log which showed a constant increase in oil and gas production compared to reference wells. Two hundred and six days after the well has been put on production, the well productivity has been more than 30% higher than any offset well.The design, execution and job evaluation of the treatments are detailed in this paper, and highlight the keys to the successful treatment which turned a well initially thought to be a failure into a technical and economic success.

Increased Reservoir Contact in Cemented Multistage Completions In the Williston Basin, Using Engineered Diversion Workflow

“…In the case when all clusters have the same number of perforations (6,6,6), the cluster closest to the heel accounted for 65% of production, and the cluster closest to the toe had very minimal production. In the optimized case (6,6,8), the cluster closest to the heel still produces 43% of oil, and the rest of production is distributed more effectively between the other two clusters.…”

“…The sequenced fracturing technique described in this study is a stimulation diversion technology which can be used in a variety of completions and in-situ conditions. Several successful cases were published showing effectiveness of the sequenced fracturing technique in remedial applications in troubled completions(Rainbolt et al, 2015;Schneider et al, 2015;Madsen et. al., 2015), in re-fracturing operations(Malpani et al, 2015), in extended-perforationinterval wells(Viswanathan et al, 2014), and in conventional completions to improve cluster efficiency within the same interval(Viswanathan et al, 2014;Kraemer et al, 2014).…”

Stimulation Optimization Using Engineered Diversion Workflow to Increase Wellbore Contact in Cemented Completions

“…Several static fluid loss tests proved the superior performance of the Composite Pill over rock salt and benzoic acid flakes (Rainbolt et al, 2015). Particles with 4 different and specific sizes in combination with special fibers are proven to be the most effective diverting agent in the industry.…”