Multi-Year Scale Inhibition from a Solid Inhibitor Applied during Stimulation

Abstract

Multi-year scale inhibition is the desired outcome from placing a scale inhibitor composite in a formation during the fracturing process. Traditionally liquid inhibitors applied through a squeeze have provided inhibition for up to one year. Deepwater operators, especially, desire longer inhibition periods. This paper reports on the twenty-four wells that have been treated for at least sixteen months. It also details the inhibition for two deep water wells that have been on line for about one year. At the time of the publication of the paper over five hundred wells have been treated with the solid inhibitor. The longest documented treatment has been in the ground for over three years. Placing a scale inhibitor composite into the formation via the fracturing process requires a product that is compatible with the fracturing fluid, does not adversely affect the conductivity of the proppant pack and provides multi-year inhibition through the controlled release of the inhibitor into the produced water. The solid inhibitor is added to the fracturing proppant. Primarily this is a mass-balance process by which a finite amount of inhibitor desorbs over time. The goal is to maximize the inhibitor loading without negatively impacting the stimulation effectiveness. Mineral scale deposition in the treated wells has not occurred in the time since the initial stimulation and inhibitor placement. In all wells, but especially for deep water wells where subsequent intervention represents a significant cost, this technology has financial benefit compared to traditional treatments. All treated wells continue to show scale mitigation, as measured by inhibitor residual in the produced water. Mineral scale deposition in wells means costly well remediation. This means decreased production and workover costs. It has an adverse impact on lifting costs. This chemical technology advancement extends the period between remedial workovers well beyond traditional expectations. It will save operators money and may encourage the development of fields that might otherwise be viewed unprofitable or marginal. Introduction Below is a brief discussion on scale inhibitor work reported upon in previous SPE papers. These all involve the addition of a scale inhibitor as a bulk fluid or solid. Only papers that reported on post-treatment measurement of scale inhibitor residual as a function of time or cumulative water production are shown. These papers report on the addition of scale inhibitor asa liquid squeeze separate from a hydraulic fracturea liquid inhibitor in a hydraulic fracture fluida solid inhibitor in a hydraulic fracture fluid These are presented as a representation of the evolution in the industry towards gaining prolonged inhibition through a single application. These bulk placements are done for two reasons. First, it is not always possible to treat for scale with a continuous treatment fed into the well bore. Second, it is preferable to place the inhibitor in the formation in order to prevent scale precipitation in the formation and to have the inhibitor in the produced water before that water reaches the pressure drop zone (zone of scale precipitation) at the near well bore. Martins (1992) reports on the addition of a liquid scale inhibitor in a hydraulic fracture fluids in Alaskan wells Alaska at Prudhoe Bay. They report on the treatment of 75 wells all of which reported acceptable inhibitor residuals up to and beyond one year. The paper shows data on acceptable inhibitor residuals after 200,000 bbls of cumulative water production on a typical well. Norris (2001) reports on the addition of a SIIP (scale inhibitor impregnated proppant) to a well in the British sector and a well in the Norwegian sector of the North Sea. For the first they report 55 days of acceptable inhibitor residuals. For the second they report 33,000 bbls of cumulative water production with acceptable residuals.

Research of Scale Inhibitors in Downhole Equipment

“…In the process of oil production in various elements of the oilfield system, inorganic salts may be deposited from the formation waters [7]. Salt formation is noted in wellhead equipment, discharge lines of wells, metering installations; However, most often this process takes place in production wells, which leads to deposition on working parts and surfaces of ESP, as well as other hydraulic machines, dense, stone sediment of 0.5-1.0 mm thick [8].…”

The state of the art in scale inhibitor squeeze treatment

“…These proppants are then incorporated into the fracture fluids and injected during hydraulic fracturing. Several articles reviewed the pro and cons of solid inhibitor in hydraulic fracture fluids (Gupta et al 2008(Gupta et al , 2010. It is critical to place the solid inhibitors uniformly in the fractures, and the secret relies on proper control of the injection flow rate and pressure.…”

Gulf of Mexico Frac-Pack with a 10% Loading of an Intermediate Strength, Chemical-Infused Proppant-Sized Particle Designed to Provide Long Term Inhibition for Barium Sulfate Scale

“…The fluid was initially sheared at 100 sec -1 , followed by a shear rate sweeps of 100, 80, 60 and 40 sec -1 to calculate the power law indices n′ and K′. The fluid was sheared at 100 sec -1 between shear rate sweeps, and the shear rate sweep was repeated every 30 minutes (Berry et al 2009;Smith et al 2009;Gupta et al 2008). The fluid formulation was listed in table 3.…”