One person's trash is another's treasure.
Whenever one drills a hole, disposal of whatever used to occupy that hole will be necessary. The bigger the hole, the higher the production - not of oil and gas, but of cuttings. Additionally, changing regulations are making disposal of large volumes of drill cuttings more challenging, particularly offshore.
Companies also are setting stricter guidelines for disposal of oilfield wastes. As part of BP's Green (Growth while Reducing Environmental Emissions Now) program:
• discharge of cuttings contaminated with oil-based muds is prohibited;
• discharge of cuttings contaminated with synthetic-based muds will be eliminated by 2003; and
• discharge of all muds and cuttings will be eliminated by 2005 (with the exception of surface hole cuttings).
To drill a typical 10,000-ft (3,050-m) well, about 6,000 bbl to 8,000 bbl of drilling mud and 3,000 bbl to 4,000 bbl of cuttings require some kind of disposal. What is to be done with all that mud and cuttings if discharge is out of the question?
Reinjection
Cuttings reinjection is one popular method of disposal. Cuttings are ground to the size of frac sand, and water and viscosifiers are added to make a slurry that is pumped into the well annulus or other zones that are isolated from the reservoir and groundwater.
Injection of cuttings down the well annulus can be done at rates of 1 bbl/ min to 6 bbl/min for a total volume of 5,000 bbl to 50,000 bbl of slurry, said Dr. Richard Keck of Pinnacle Technologies. If a dedicated injection well is used (usually onshore), rates of 5 bbl/min to 20 bbl/min can be achieved, disposing of millions of barrels of cuttings in a single well. "There is even a skid-mounted unit complete with mixer, shear pump for grinding, holding tank and triplex injection pump," the Society of Petroleum Engineers distinguished lecturer said. "It's not exactly high-tech. In fact, it's fairly routine."
It's amazing how large a volume of cuttings can be pumped downhole. At the Thums field in Long Beach, Calif., 100 cu yd of cuttings were injected daily. In Texas, 20,000 b/d were reinjected into 10 wells at a rate of 25 bbl/min, after being ground up with a ball mill. In Alaska, 24,000 b/d of slurry was reinjected. "The process is similar to hydraulic fracturing and is subject to potential screenout," Keck said, recommending lots of small batches to form multiple fractures for storing the cuttings, rather than one single injection.
Other options
Operators need to think outside the box when considering disposal options for drilling fluids and cuttings. Disposal in hollowed-out salt domes is being discussed, and Louisiana is planning to release new rules concerning that option this quarter.
Perhaps a new revenue stream could be created if clean cuttings were sold for useful purposes rather than dumped overboard. Carla Suite, environmental project engineer at BP Trinidad and Tobago LLC, suggested the following:
• artificial reefs - pilot tests are being performed on the use of drill cuttings for creating offshore structures for flora and fauna;
• coastal protection - construction of berms can reclaim beaches lost to hurricanes, and cuttings are being considered for use as a substrate for wetland vegetation in the Gulf Coast region;
• soil conditioning - the alkaline nature of drill cuttings makes them suitable for neutralizing acidic soils;
• landfill cover - treated drill cuttings have been used as municipal landfill for 10 years to prevent disease, fires and odors;
• construction - drilling residue has been used in cold and hot asphalt, concrete and bricks; and
• ceramics - clean cuttings can be used in fired clay products such as pottery and tiles.
Of course, economical, logistical, environmental and liability concerns would have to be addressed for each option.
Hart's E&P would like to provide a forum for the exchange of ideas on how to dispose of drilling wastes in an environmentally and economically sound manner. Send me your ideas and success stories so I can share them with others around the world.
Good news in Canada
According to the Petroleum Services Association of Canada (PSAC), drilling activity in western Canada is not slowing even though oil and gas prices are down. Canadian operators still plan to drill 18,205 wells this year, including 10,720 gas wells, 5,288 oil wells and probably 1,961 dry holes, estimates that are much the same as this past spring. "The larger oil and gas producers have indicated to us that they will be completing their planned 2001 drilling programs," said Roger Soucy, president of PSAC, the national trade association of 240 contractors to oil and gas companies. "At current prices, it is still profitable to bring these commodities to market." This year's drilling activity is 15% higher than last year in Alberta and Saskatchewan and more than 30% higher in British Columbia.
Tax refund
According to The Scotsman, about 20,000 offshore workers employed on drilling rigs in British waters are due substantial rebates after the Court of Appeal in London ruled jackup rigs should be classed as ships for tax purposes. Rig hands will be entitled to the same tax breaks as seafarers, who are exempt from tax on money earned outside the country, provided they comply with length of residence rules. Workers' rebates will average US $7,370 (£5,000).
Three Santa Fe jackup rig employees set a precedent that is expected to lead to a flood of similar claims by other drilling company employees. Although the General Commissioners (who rule on tax disputes) had originally decided the men were seafarers, the Inland Revenue took the case to the High Court, where a judge ruled a jackup rig was not a ship because it had legs and did not actually float when in position. The three men then set up a fighting fund among fellow North Sea workers to take their case to the Court of Appeal, where they won their case. Workers employed on semisubmersibles and drill ships already receive tax concessions.

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