Are Slick-Water Fracturing Applications Effective in the J-Sand Formation?

Abstract

Since the early 1970s, fracturing fluid systems utilized in the J-Sand treatments in the Wattenberg field have ranged from poly emulsion to cross link gels with and without an inert gas phase (e.g. N2, CO2). Current treatments typically consist of large proppant volumes and crosslinked fluid volumes (e.g. 500,000 lbs and 7,000 barrels). Large treatment volumes results in large job costs for the well operators who have searched for ways to reduce treatment costs without sacrificing well production. Also in early 2000, large treatments were resulting in poorer productive J-Sand wells due to suspected pressure depletion. In 2002, one well operator in the Wattenberg field implemented an alternative method to stimulate the J-Sand:substituting the slick water based fluid for the massive crosslinked gel based fluid andreducing the proppant volume by as much as 4.5 fold. This strategy reduced job costs significantly without impacting ultimate gas recovery. At the end of 2002, the well operator completely switched over to the slick water treatments (SWT) for the J-Sand interval. By lowering the completion costs of a J-Sand well, many additional wells will be drilled that otherwise would not be economic. In this paper, the production from eight J-Sand wells stimulated with SWT will be compared to the 15 offsetting wells stimulated with crosslinked gel treatments (CGT).Production analysis methods will be utilized to determine reservoir and fracture flow capacity (e.g. drainage area, kh, effective fracture half length) for the wells considered in this case study. Also, treatment pressure history matching will be performed for selected wells to evaluate the resultant fracture geometry of the different styles of treatments. Introduction Field Description. The Wattenberg field is located 25 miles north of Denver, Colorado (Figure 1). The field encompasses 980 square miles in Boulder, Broomfield, Weld and Adams counties in the western portion of the Denver Julesberg (DJ) Basin. To date, in the Wattenberg field, the J-Sand formation has produced over 14.0 TCF of gas and 42.66 million barrels of oil. Typical well spacing in the Wattenberg field was 160 acre spacing for all wells until 1998. The Greater Wattenberg Rule (318A), effective in May of 1998, permitted up to ten Cretaceous wells per 320 acre block. This allowed Operators to deepen a 7,100-foot Codell well bore just +/-500 feet to the J-Sand for a fraction of the cost of drilling a grassroots well. Because of the Rule, many Operators in the Wattenberg field began a J-Sand infill drilling program. Typically, operators are infill drilling at a density of five J-Sand wells per 320-acre unit[1]. The challenge to the infill drilling of J-Sand wells by the operators was now two-fold:continue with economical fracture treatments on the increased number of J-Sand wells andcontinued economic J-Sand production from a formation that has been productive since the early 1970s. Geology The J-Sand formation in the Wattenberg field is classified as a "tight" gas sandstone of Cretaceous age. The J-Sand comprises the upper portion of the Dakota Group in the Wattenberg field. The lower contact (gradational) is with the marine shales of the Skull Creek formation. The upper contact (sharp and erosional) is with the marine units of the Mowry Shale formation. The J-Sand is divided into two members, the older Fort Collins Member and the upper Horsetooth Member. Within the Wattenberg proper the Horsetooth member is typically thin or absent which leaves the Fort Collins member as the primary producer in the majority of the Wattenberg field. The Horsetooth member was deposited in a fluvial and estuarine environment that has resulted in less lateral and vertical deposits when compared to the Fort Collins member.

Effects of salinity and temperature on drag reduction characteristics of polymers in straight circular pipes

“…Slick-water fracturing has the advantages of reducing job costs significantly without impacting ultimate recovery over conventional polymer. Due to low viscosity of slick-water, higher pump rates are needed to create the fracture width necessary to place proppant and avoid screen-out (Shaefer, 2005;Britt et al, 2006;Mills, 2006)). With the universal trend of using small diameter pipes (especially in coiled tubing applications), reduced pipe diameters (and secondary flows in coiled section of the tubing) generate high friction pressure losses, thus limiting the pumping capacity.…”

Experimental Investigation of Cryogenic Fracturing of Rock Specimens Under True Triaxial Confining Stresses

“…Massive hydraulic fracturing has been demonstrated as one of the most effective technologies and are widely applied in combination with horizontal drilling for developing shale reservoirs (Steward 2013). Due to the general availability and low cost of water, fracturing fluids of hydraulic fracturing are mostly water-based, containing proppants and some chemical additives (Sharma et al 2004, Shaefer 2005.…”