September 2000 Supplement  Case Study

Company-operated, integrated, E&P waste management facility reduces costs

John Nussbaumer, Patina Oil & Gas Corp.

Bottom line. An integrated, E&P waste management facility has reduced Patina Oil & Gas Corp.’s costs for processing oil-contaminated soils and fluids, including tank bottoms. Disposal costs have been lowered from $20/yard, with liability attached, to under $4/yard, without the liability. With reuse of treated soil, cost of the landfarming operation is breakeven.

Background. Patina operates approximately 3,000 wells in the Greater Wattenberg field of the Denver-Julesburg basin. When evaluating E&P waste management options, two factors led to the company’s decision to design, permit, construct and operate its own waste management facility. First, E&P waste disposal at commercial facilities is expensive – about $20/ton of oily solids at a nearby commercial facility. And some facilities would not take soil with more than 1% hydrocarbons. This contamination level is the clean-up standard under Colorado Oil and Gas Conservation Commission (COGCC) standards applicable to non-sensitive areas.

Liability was another important consideration. Commercial facilities tend to be under-capitalized and operated "on the cheap." When things go wrong, as they have at one local facility that has been determined to represent an "imminent and substantial endangerment" under the Resource Conservation & Recovery Act, operators can become liable. Under RCRA, EPA has mandated a full investigation and remediation of the example site, and its operator has declared insolvency. Oil and gas operators may be liable for up to $3 million.

Considering these factors, Gerrity Oil & Gas, a predecessor to Patina, chose to pursue the company-operated E&P waste management facility option. The facility was to allow bioremediation of contaminated soil through landfarming, plus provide sludge treatment capability for oily drilling muds, tank bottoms and other sludges. Incoming sludge would be separated into salable product, clear water and residual solids, which would be incorporated into the landfarm for bioremediation.

Early in the permitting process, Gerrity encountered a dual jurisdictional problem between COGCC and the Colorado Dept. of Public Health and Environment (CDPHE). Ultimately, legislation specifying that COGCC had sole jurisdiction for "noncommercial" facilities was required. COGCC defines noncommercial as those accepting only E&P waste from one operator, or from a unitized area under a joint operating agreement. Even then, facilities must comply with local land use regulations.

Treating process. The processing facility contains two 340- by 105-ft soil-treatment cells. Soil that is not totally saturated with hydrocarbons is placed directly into one of the cells. "Dripping wet" saturated soils are placed into the sloped-bottom cement pit. At the lowest end of this pit, there is a chamber with a baffle to allow separation of oil and water. Tank bottoms or BS&W are pumped into either the open tank for immediate processing or into a 300-bbl storage tank for later processing. Material in the open tank is allowed to set for 24 hours to allow oil and water to separate. Oil is then pumped off to a tank fitted with an internal heater and heated to 160°F. The majority of the water is pumped into a lined pit fitted with a sprinkler system for evaporation. In the future, this water will be used to irrigate the treatment cells, thus speeding up the bioremediation process.

Oil from the heated tank is pumped through a heater treater for further separation. If needed, chemicals are added to assist separation. Separated oil is routed to the sales tank and water to the evaporation pit. To date, about 3,000 bbl of salable oil have been separated, bringing revenue that helps defray operational costs. Residual solids are flushed out with water and routed to a sloping cement pit for mixing with soil, which is then spread in the treatment cells.

Landfarming process. To be degraded, crude oil requires catalysis by microbial enzymes and/or environmental modification. Environmental modifications can include suitable temperature, moisture, nutrients, pH adjustment, sunlight, oxygen and catalysts that break the hydrocarbon bonds making microbial action easier. In this facility, Patina incorporates sunlight, oxygen, suitable temperature and nutrients.

Soil placement in the cells is limited to depths of 12 to 18 in., since with greater depths, mechanical tilling is inadequate and the soil does not receive adequate aeration. To accelerate bioremediation, soil is tilled with a tractor pulling a cultivator twice a week. Initially, Patina tilled the soil a couple times a month and realized remediated soil (< 1,000 ppm) in nine months to a year. With twice weekly tilling, remediated soil is achieved in less than 90 days.

To preserve temperature during winter months, a road grader windrows the soil. Optimum pH range for bioremediation is 6.5 to 9.5; pH of the cells has ranged from 6.91 to 8.96. To date, Patina has not added moisture. For bioremediation, optimum moisture content is in the 20 – 30% range. Nitrogen and phosphorus nutrients are needed for the bioremediation process. Patina uses turkey manure, which is available locally for transportation cost only. To date, Patina has not had to use a bioremediation catalyst, which could reduce treating times to 30 – 45 days.

The Colorado Oil and Gas Conservation Commission and the Weld County Health Department require sampling of the soil remediation cells – semi-annually for oil and grease and pH, and annually for RCRA metals. Results for both cells are shown in Table 1. Heavy metal constituents are consistently well below regulatory levels. For example, the barium (a common contaminant in oilfield waste) levels well below 100 ppm are far below the regulatory level of 180,000 ppm. Sampling must be conducted annually for TPH 5-ft below ground. It was nondetectable during 1997 and 1998. All remediated soil is sampled prior to release. No soil is released unless hydrocarbons are below 1,000 ppm, and generally they are below 600 ppm.

Remediated soil is moved from the remediation cell to a staging area to be reused on field locations. Normally, this soil is used on lease roads, building up berms, replacing hydrocarbon-impacted soil in excavations and in building locations where needed. Soil that is brought into the waste management facility is accompanied by documentation showing where the soil came from. Similarly, documentation is kept on the final disposition of the remediated soil.

Economic benefits. Patina has incorporated successful, accelerated bioremediation of hydrocarbon-impacted soil and treatment of tank bottoms, which is producing salable crude oil and reusable soil – all at one central facility. Disposal costs have gone from $20 per yard of soil, with liability attached to less than $4 per yard, without the liability. With the reuse of the treated soil, the cost of the landfarming operation is a breakeven process for Patina.

Factors influencing whether landfarming would be attractive for other operators include:

• State / local regulations
• Availability of land
• Ground water or other environmental concerns where land is located
• Number of wells / size of operations.

In Colorado, if a company already owns the land and there are not groundwater / other environmental factors, the threshold size for landfarming operations could be in the 400 to 500-well range, depending on company circumstances.

Acknowledgment

This information has been presented, through an extended paper and field trip, as part of the "2000 Hazardous Waste Research Conference," May 25 in Denver, Colo.