Abstract
The major oilfield processes that can influence the environment are drilling and production. Different materials are used in both processes, and waste is generated. Some of this waste can have significantly harmful effects on the environment; thus, it is necessary to responsibly manage created waste. In virtually all cases, harmful effects can be minimized or eliminated through the implementation of proper waste management. The selection of the method to manage Exploration and Production (E&P) waste depends on laws and regulations, the ecosystem of the location where the operations take place, and the cost-effectiveness of the selected procedures. The most widely used method for the disposal of most petroleum industry waste is underground injection, which enables the permanent disposal of waste slurry by injecting it into a suitable subsurface disposal zone. Performing underground waste injection in a safe, cost-effective manner requires experience, skill, and resources.
TopBackground
Drill cuttings injection began in the mid-1980s with small volume annulus injection in the Gulf of Mexico (Malachosky, Shannon, Jackson, 1991). By the early 1990s, its use had broadened in the Gulf of Mexico (Louviere & Reddoch, 1993), the North Sea (Minton, Meader & Willson, 1992;Minton & Secoy, 1992; Willson, Rylance & Last, 1993; Moschovidis, Gardner, Sund & Veatch, 1993; Sirevåg & Bale, 1993; Crawford & Lescarboura, 1993; Schuh, Secoy & Sorrie, 1993; van Gils, Thornton, Kece, Bennet & Yule, 1995), Alaska (Schumacher, Malachosky, Lantero & Hamilton, 1991) and the Mediterranean (Reddoch, Taylor & Smith, 1995) as a cost effective option to comply with environmental waste disposal regulations.
In South Texas (Gardiner, 1994), naturally occurring radioactive material (NORM) was disposed of in subsurface formations. In the mid-1990s, the first large commercial facility with dedicated injection wells began operation (Marinello, Lyon & Ballantine, 1996). This event was followed by large-scale injection operations in Alaska (Schmidt, Friar, Bill & Cooper et al., 1999) and the Gulf of Mexico (Baker, Englehardt & Reid, 1999a, Baker, Englehardt & Reid 1999b; Reed, Mathews, Bruno & Olmstead, 2001).
Key Terms in this Chapter
Hydraulic Fracturing: The creation of fractures within a reservoir that contains oil or natural gas to increase flow and maximize production or within a disposal formation to accommodate injected slurry. A hydraulic fracture is formed when a fluid is pumped down the well at pressures that exceed the rock strength, causing open fractures to form in the rock.
Tubular Injection: A form of slurry injection that introduces the waste slurry through the tubing and injection to either a section of the drilled hole that is below all casing strings, or to a section of the casing that has been perforated at the depth of a disposal zone.
Disposal Domain: The area within the disposal formation around the injection point, created by hydraulically induced fractures, which accumulate the bulk volume of solids from repetitive waste slurry injections.
Formation or Geological Formation: A layer of rock that is made up of a certain type of rock or a combination of types.
Annular Injection: A form of slurry injection that introduces the waste slurry through the space between two casing strings (known as the annulus).
Tubing: A small-diameter pipe installed inside the casing of a well that conducts injected fluids from the wellhead at the surface to the injection zone and protects the long string casing of a well from corrosion or damage by the injected fluids.
Confining Zone: A geological formation (or group or part of a formation) capable of limiting fluid movement out of an injection zone. The ideal confining zone has low permeability and sufficient thickness to prevent upward movement of injected waste.
Cuttings Re-Injection (CRI): A waste disposal technique where drill cuttings and other oilfield wastes are mixed into a slurry with water and pumped at high pressure into hydraulically created fractures up to several thousand meters below the surface (also known as Drill cuttings re-injection (DCRI) or Waste injection (WI) ).
Waste Slurry: A suspension of solids (cuttings) in water. It usually contains solids of size less than 300 microns (0.3 mm) in concentration of 20 to 30 percent by volume.
Injection Zone: A geological formation, group of formations, or part of a formation that receives fluids through a well (known as the disposal zone).
Batch Volume: A volume of slurry continuously injected at one time.