Safe Disposal of One Million Barrels of NORM in Louisiana Through Slurry Fracture Injection
- A.C. Reed (Terralog Technologies Inc.) | J.L. Mathews (Chevron USA) | M.S. Bruno (Terralog Technologies Inc.) | S.E. Olmstead (Terralog Technologies Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- June 2002
- Document Type
- Journal Paper
- 72 - 81
- 2002. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 6.5.3 Waste Management, 6.5.4 Naturally Occurring Radioactive Materials, 3 Production and Well Operations, 4.1.5 Processing Equipment, 1.2.2 Geomechanics, 4.3.4 Scale, 4.2 Pipelines, Flowlines and Risers, 5.6.4 Drillstem/Well Testing, 2.5.1 Fracture design and containment, 1.2.3 Rock properties, 2.4.3 Sand/Solids Control, 5.6.1 Open hole/cased hole log analysis, 2.2.2 Perforating, 1.11 Drilling Fluids and Materials, 3.2.5 Produced Sand / Solids Management and Control, 1.14 Casing and Cementing, 1.6 Drilling Operations, 2 Well Completion, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 7.1.9 Project Economic Analysis, 7.1.5 Portfolio Analysis, Management and Optimization, 5.6.5 Tracers, 7.1.10 Field Economic Analysis
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During the past 50 years, storage pits and adjacent land around the Bay Marchand facility near Port Fourchon, Louisiana, had accumulated large deposits of nonhazardous drilling and production waste containing naturally occurring radioactive material (NORM). This material primarily included drill cuttings, drilling mud, produced sand, salt water, pipe scale, crude oil, and precipitates. To remediate this site, the operator chose to reinject the material into the deep subsurface through on-site slurry fracture injection (SFI). This process provided greater environmental security compared to alternative surface pit or landfill disposal and at a much lower cost than off-site transport and disposal options.
More than 1 million barrels of pit soil and canal bottoms were safely disposed into a single well during 2 years of injection that concluded in March 2000. Solid waste was mixed with water to create a slurry and injected downhole at greater than the formation parting pressure into a weakly consolidated sandstone formation at depths from 4,400 to 5,000 ft. Injection operations were episodic, generally taking place for 11 hours per day, 5 days per week. This allowed the formation pressure to decline each day to the initial reservoir pressure. The project was designed and extensively monitored to maintain and verify containment within the permitted interval. Downhole pressure was continuously monitored, allowing analysis of daily falloff pressure. Waste containment was confirmed through a combination of shut-in pressure analysis and periodic step-rate tests, gamma logs, and temperature surveys.
In addition to the improved environmental protection provided by this technology, the on-site operation was a fraction of the off-site disposal costs. This paper describes the project design and permitting, injection operations, containment monitoring and analysis, and project economics.
The Bay Marchand oil field is located just offshore southern Louisiana and began production in 1949. Oil production came onshore at the Bay Marchand Terminal in Port Fourchon (Fig. 1). Oil production was processed through a series of pits into the 1980s to separate water and other materials from the oil. Over time, the pits accumulated drill cuttings, drilling mud, produced sand, salt water, pipe scale, crude oils, and precipitates, all of which contained small amounts of NORM.1,2 The elements of concern were uranium- 238, thorium-234, and radium-228.
The three processing pits were located at the east end of the California Canal (Fig. 2). These pits were hydraulically isolated, preventing any radioactive materials from leaching into the adjacent canal, particularly radium, which is very soluble in salt water. To the southeast, the Dead End Canal also contained substantial quantities of NORM and nonhazardous oilfield waste (NOW) mixed into canal bottom soils. This contamination was primarily caused by overflows from discharge and processing pits at the material-handling facility located adjacent to the canal.
The remediation project was composed of two phases - excavate and backfill the Bay Marchand pits and remediate the bottom of the Dead End Canal. The Bay Marchand pits were excavated between October 1997 and September 1998 with the material injected into a disposal well, City of New Orleans #2 (CNO#2), with the SFI process. The Dead End Canal was drained and excavated from February 1999 to March 2000. The canal bottom was excavated to an average depth of 6 ft and a maximum of 12 ft in any given area. A total of 371,600 bbl of material were excavated from the Bay Marchand pits, and 623,100 bbl of canal bottoms were excavated from the Dead End Canal.
In addition to the pit and canal materials, small volumes of tank bottoms, produced water, and other NORM-contaminated production wastes were disposed in Well CNO#2. The total volume of these nonhazardous oilfield wastes was 20,970 bbl of liquids and 6,120 bbl of solids. The total volume of solids disposed over the course of the project was 1,000,800 bbl contained in 2,949,700 bbl of slurry.
SFI was the chosen disposal technique because it provided permanent NORM disposal, minimized environmental liability, and was the most cost-effective of the options considered, particularly when compared to barging the solids to a NORM-approved landfill.
Many types of oilfield waste that are integrally associated with exploration and production activities, such as drill cuttings, produced sand, tank bottoms, sump material, and crude-contaminated surface soil, can be economically disposed of in an environmentally sound manner through reinjection into an appropriate subsurface formation. In this process, solids are mixed into a slurry with fresh or produced water and injected at a high pressure into suitable sand formations. The carrying fluid bleeds off rapidly, leaving behind a pod of solid waste permanently entombed by natural Earth stresses. Soluble materials remain within the target sand formation because the overlying shales have very low permeability.
On-site, deep-well injection of exploration and production (E&P) wastes provides significant environmental and economic advantages over traditional landfill disposal for oilfield wastes. These include:
Improved protection for surface and groundwater.
Little impairment of surface land use.
Reduced long-term liability risk to the waste generator.
Reduced transportation and disposal costs.
The use of deep-well injection has expanded significantly in recent years. For example, large-scale E&P waste-injection operations have taken place in Canada,3 Alaska,4 California,5 and the North Sea.
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:
Maintain waste containment in the target formation (environmental management).
Sustain long-term injectivity with minimum equipment repairs and well workovers (cost management).
Maximize formation storage capacity and well life (asset management).
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