Environmental Management, Cost Management, and Asset Management for High-Volume Oil Field Waste Injection Projects

Abstract

fax 01-972-952-9435. AbstractOngoing exploration and production activity, combined with increased regulatory requirements, are increasing the volume and costs associated with disposal of oil field wastes, including produced oily sands and tank bottoms, drilling mud and cuttings, crude contaminated surface soils, and naturally occurring radioactive materials (NORM). A cost-effective and environmentally sound disposal option is to re-inject waste material into the subsurface into non-productive and/or depleted zones under controlled fracture conditions. High volume injection projects often involve annual injection exceeding several hundred thousand barrels of waste for several years. The critical engineering management goals for such operations are to: 1) Maintain waste containment in the target formation (environmental management);2) Sustain long-term injectivity with minimum equipment repairs and well workovers (cost management); and3) Maximize formation storage capacity and well life (asset management).More than five years experience operating, analyzing, and managing large volume waste injection projects in the US and Canada has enabled Terralog to develop specific design, monitoring, and operating strategies to achieve these goals. Target injection formations must be selected with appropriate overlying barrier and absorption zones.Offset well completions must be carefully examined. The injection well completion should be appropriately designed to take into account high formation stresses and potential movement. Continuous monitoring and analysis must be performed to evaluate varying formation properties, injectivity, stress conditions, and fracture orientation and height growth. Finally, through continuous monitoring and analysis of formation response, injection parameters and properties (such as solids concentration, density, flow rate, shut-in time, etc...) can be adjusted in order to maintain containment, reduce operating costs, and optimize long-term injectivity.

Deep Underground Injection of Waste from Drilling Activities—An Overview

“…In that sense, the injection of waste from oil and gas explorations and production activities (including waste from drilling activities) into deep subsurface formations as one of the on-site permanent waste disposal methods achieves zero discharge; improves the protection of the groundwater and surface; has a small surface footprint; reduces the need for waste transportation (via pipelines, marine vessels or tankers on-shore) and disposal costs; eliminates risks associated with the surface accumulation of generated waste and is not limited by locations [10,[18][19][20][21][22][23][24]. Besides all that was mentioned above, subsurface injections of drilling waste makes the continuous use of oil-based mud during drilling troubled shale formations in environmentally sensitive areas possible [25].…”

“…According to Bruno et al [22] from Terralog Technologies, one of the leading companies in waste slurry injection technology, there are three main engineering goals in the waste injection project:…”

“…Based on a large number of data from eight projects in the USA and Canada and the published information, Bruno et al concluded that, in large-scale injection projects, multiple fractures are likely to occur as a result of reduction in the fracture conductivity in combination with a stress increase within the waste pod. Additionally, with every newly injected volume during the intermittent injection process, a new fracture will be created with a variation in azimuth between 30° and 60° compared to the previous one [22]. There is also a possibility of the creation of a horizontal fracture during a fracture waste injection if overburden stress is or becomes less stressed because of horizontal maximum and minimum stress alterations in the disposal zone.…”

“…Well integrity of the offset well within the radius of 600 m from the injection well site is also important to prevent possible unwanted movements of the injected waste outside the injection formation and the contamination of underground sources of drinking water. According to the research conducted by Bruno et al [22], almost all contamination during the waste slurry injection process is the result of communication through an adjacent offset well because of a poor primary cementation. Some authors provide special recommendations for injection well drilling and completion design to meet the requirements of the slurry injection process itself and to ensure mechanical and hydraulic integrity.…”

“…Slurry fracture injection at pressures above the formation fracture pressure is usually used for the disposal of large quantities of waste generated during the drilling and completion phase into sandstones of relatively high porosity. On the other hand, the injection of the same slurry waste in soft formations is still relatively unexplored and usually results in various downhole problems, such as a casing collapse because of excessive movement of the soft formation and permanent pressurization and filling of the injection zone or spreading of the injected waste slurry out of target formation [22]. Although soft formations have large storage capacities, fracture modeling is always challenging, because the relationships between pressure and fracture widths are different in comparison with hard formations.…”