Minimizing Environmental and Economic Risks with a Proppant-Sized Solid Scale Inhibitor Additive in the Bakken Formation
- Steve Szymczak (Baker Hughes) | Dong Shen (Baker Hughes) | Rocky Higgins (Baker Hughes) | D.V. Satya Gupta (Baker Hughes)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 8-10 October, San Antonio, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 4.6 Natural Gas, 4.3.4 Scale, 4.2.3 Materials and Corrosion, 5.8.2 Shale Gas, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 2.2.2 Perforating, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.8 Formation Damage
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Within the past decade, hydraulic fracturing has been proven to improve the efficiency and economics of recovering oil and natural gas from shale formations. In a previous paper (SPE 134414), a summary of treatment results of placing a solid scale inhibitor into formations via the fracturing process for over five years and in over 1500 wells was fully discussed. The practice of hydraulic fracturing has come under scrutiny due to concerns about the environmental impact, health and safety. Therefore, a novel biodegradable solid scale inhibitor with an excellent ecotoxicity profile for fresh water incorporated into a solid matrix was recently developed and deployed in North Dakota. For one operator in this area with 150 Bakken-producing wells, 22 of the wells have experienced at least one event of severe mineral scaling in the pump and production tubing, leading to well failure, whereas the results from over 140 Bakken wells now fractured with the new solid inhibitor additives indicate no reported scale failures to date.
This paper provides a detailed description of the first deployment of this environmentally preferred proppant-sized solid scale inhibitor additive under severe scaling conditions in the field. In addition, an analytical method developed to track the residual of this additive in the produced fluid containing polysaccharide contaminants is also discussed.
Several methods are known in the art for introducing scale inhibitors into producing wells. For instance, a liquid inhibitor may be pumped into a water-producing zone of the subterranean formation by application of hydraulic pressure from the surface, which forces the inhibitor into the target zone. In most cases, such treatments are performed at downhole injection pressures below that of the formation fracture pressure. However, this scale squeeze operation is a non-selective process that leads to uncertainties in the extent of coverage of water-producing zones during hydraulic fracture operations. Thus as the liquid scale inhibitor is injected into the fracture, the liquid tends to be lost into the formation before penetrating any appreciable distance along the propped fracture (Norris et al., 2001). Alternatively, a liquid scale inhibitor can be incorporated into the fracturing fluid to provide initial protection against scale. However, there is little control over the release rate as measured through subsequent inhibitor residual testing.
Rather than use a liquid chemical inhibitor, the wells can be treated with a solid inhibitor. For example, a chemical inhibitor can be adsorbed onto an inert, proppant-sized, solid particle, which can be applied with a fracture stimulation operation that combines two treatments, saving the operator time and possibly expense (Gupta et al., 2010; and Brown et al., 2011). In this strategy, the solid inhibitor is placed in the created fracture, far enough from the wellbore, and distributed evenly throughout the fracture. When production begins, the inhibitor slowly desorbs into the fluids contained in the formation before such fluids enter the wellbore. More than 15,000 wells have been treated with the proppant-sized solid inhibitor during the hydraulic fracture process since 2004.
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