Waste Minimization in Drilling Operations
Waste minimization has been proven to be an effective and beneficial operating procedure. You will find that there are many economically and technically feasible waste minimization techniques that can be used in drilling operations. In fact, many oil and gas operators have implemented waste minimization techniques and have enjoyed benefits such as:
- reduced operating and waste management costs;
- increased revenue;
- reduced regulatory compliance concerns;
- reduced potential liability concerns; and
- improved company image and public relations.
Choosing feasible source reduction and recycling options (i.e., waste minimization) is a smart business decision.
Waste minimization is part of the concept of the "Waste Management Hierarchy." The Waste Management Hierarchy sets out a preferred sequence of waste management options. The first and most preferred option is source reduction. Source reduction is any activity that reduces or eliminates either the generation of waste at the source or the release of a contaminant from a process. The next preferred option is recycling. Recycling is the reclamation of the useful constituents of a waste for reuse, or the use or reuse of a waste as a substitute for a commercial feedstock or as a feedstock in an industrial process. Together, source reduction and recycling comprise waste minimization. The last two options of the hhierarchy, and least preferred, are treatment and disposal.
This document provides a general overview of waste minimization techniques for wastes arising from oil and gas drilling operations. In addition to a discussion of waste minimization techniques for drilling waste, the document provides case histories of successful waste minimization projects and a bibliography of useful technical references. Many of the references listed in the bibliography provide detail on the successful application the waste minimization opportunities discussed in this document.
The Railroad Commission also provides the publication Waste Minimization in the Oil Field. Waste Minimization in the Oil Field provides a general overview of waste minimization as a waste management practice and how to include it in an area-specific waste management plan. It also includes chapters on waste generation in oil and gas operations, identification of hazardous oil and gas waste, and the principles of waste minimization. Waste Minimization in the Oil Field is available from the RRC's Waste Minimization Program.
Waste Minimization in Drilling Operations
As noted in the introduction, there are many economically and technically feasible waste minimization techniques that may be applied to drilling operations. An operator should consider all costs, including waste management and disposal costs, when evaluating the feasibility of a waste minimization option. For example, a substitute product or chemical may cost more, but the savings in waste management and disposal costs will make the substitution cost-effective.
The following discussion will consider the various source reduction opportunities for wastes arising from a drilling operation.
The best place to start waste minimization efforts for a drilling operation is in the planning stages. The drilling plan should be evaluated for potential waste generation and modified to take advantage of the other source reduction and recycling options discussed below. A discussion of anticipated waste generation and management should be an integral part of the pre-spud meeting. This preplanning can make a significant impact on the waste management requirements of the drilling operation.
- Drill Site Construction and Rigging-Up - A preplanning opportunity for a drilling operation is in the construction of the location and roads. The drilling location and the associated roads should be planned so that they are constructed such that stormwater runoff is diverted away from the location and that the location's stormwater runoff, which may be contaminated, is collected. Construction of the location and roads should be planned so that erosion is minimized. These steps will help minimize the volume of contaminated stormwater runoff to be managed. Also, the location size should be only as large as absolutely necessary. Location construction costs, including the cost of the disposition of cleared trees and vegetation, can be reduced. Also, the image of such an operation, as perceived by the general public, is enhanced.
- Drilling Fluid Systems - An operator should design the drilling fluid system with waste minimization in mind. Several waste minimization opportunities for drilling fluid systems, such as improved system monitoring, substitute fluids and improved solids control, are discussed under the remaining opportunities. These waste minimization techniques should be integrated into the drilling fluid system portion of the drilling plan.
- Pit Design - Another consideration in preplanning for a drilling operation is the design of the reserve pit. (Also lso see "closed-loop" drilling fluid systems under procedural changes.) A major oil company has designed a V-shaped pit that provides advantages with respect to waste generation and operational costs. The open end of the "V" faces the drilling rig and the cross-sectional view looks like a squared-off funnel (about 10 feet deep with the upper 5 feet having slanted walls to a width of about 20 feet). This V-shape design prevents mud from channeling from the discharge point to the suction point, as it must travel the full length of the pit. Also, because the V-shaped pit is long and narrow (each leg is about 110 feet long), it is easier to construct and line, if necessary. In an actual comparison to a conventional reserve pit (for drilling similar wells using the same drilling rig), the company determined that pit construction time was reduced by about 40%, water costs for the well were reduced by about 38%, and the liner costs were reduced by about 43%. The total cost savings were about $10,800. Also, the use of water was minimized (which is applicable under the waste minimization opportunity ). The V-shaped pit also leaves a smaller "footprint."
Product substitution is one of the easiest and most effective source reduction opportunities. Vendors are becoming more attuned to operators' needs in this area and are focusing their efforts on providing less toxic, yet effective, substitutes. Some operators have found that vendors and suppliers will start offering less toxic substitutes in response to a company's establishing inventory control procedures. A few examples of effective and beneficial product substitution for drilling operations are provided below.
- Drilling Fluids - Many companies have found that the substitution of low toxicity glycols, synthetic hydrocarbons, polymers, and esters for conventional oil-based drilling fluids is an effective drilling practice. The use of substitute drilling fluids eliminates the generation of oil-contaminated cuttings and other contamination by the oil-based fluid (e.g., reserve pit and accidental releases). Drill site closure concerns are also reduced. Drilling engineers have published numerous technical papers that describe the successful application of substitute drilling fluids. In many instances, this substitution has resulted in significant cost savings. Also, substitute spotting fluids are available for freeing differentially stuck drill pipe.
- Drilling Fluid Additives - Many of the additives used in the past for drilling fluids have contained potential contaminants of concern such as chromium in lignosulfonates. Also, barite weighting agents may contain concentrations of heavy metals such as cadmium or mercury. The use of such additives has diminished. However, an operator should take care to select additives that are less toxic and that will, therefore, result in a less toxic drilling waste. The design of the drilling fluid system is the best place to implement this product substitution opportunity.
- Pipe Dope - Pipe connections require the use of pipe dope. American Petroleum Institute (API) specified pipe dope contains about 30% lead by weight and, therefore, can be of concern when disposed of. One simple waste minimization technique is to ensure that all pipe dope is used and containers are completely empty. However, lead-free, biodegradable pipe dopes are now available and, if feasible, should be substituted for API specified pipe dope. Even if API specified pipe dope is necessary for making the required connections, pipe supply companies should be asked to provide pipe with lead-free pipe dope on the thread protectors. That way you can recycle the thread protectors with fewer regulatory concerns.
- Organic Solvents - Organic solvents, such as trichloroethylene, and carbon tetrachloride, are commonly used for cleaning rig equipment and tools. These solvents, when spent, become listed hazardous oil and gas wastes and are subject to stringent regulation. Alternative cleaning agents, such as citrus-based cleaning compounds and steam may be substituted for organic solvents. By doing so, a hazardous waste stream may be eliminated, along with the associated waste management and regulatory compliance concerns. Another solvent commonly used on drilling rigs is Varsol (also known as petroleum spirits or Stoddard solvent). While most Varsol has a flashpoint below 140oF, which is a characteristically hazardous waste when spent, some suppliers may provide a "high flash point Varsol" with a flash point greater than 140oF. Ask for non-toxic cleaners that reduce your regulatory compliance concerns.
- Paints and Thinners - Oil-based paints and organic solvents (i.e., thinners and cleaners) are used less frequently today, nonetheless they are still used. These paints and thinners provide an excellent product substitution opportunity. Water-based paints should be used whenever feasible. The use of water-based paints eliminates the need for organic thinners, such as toluene. Organic thinners used for cleaning painting equipment are typically listed hazardous waste when spent. This substitution can eliminate a hazardous waste stream and reduce waste management costs and regulatory compliance concerns.
Lubricating Oil Purification Units
The drilling rig's diesel power plants typically generate large volumes of waste lubricating oil and lubricating oil filters. A lube oil testing program combined with extended operating intervals between changes is effective. However, an equipment modification also can effectively reduce the volume of waste lubricating oil and filters. Commercial vendors offer a device called a lube oil purification unit. These units use 1 micron filters and fluid separation chambers and are attached to the lube oil system of an engine. The unit removes particles greater than 1 micron in size and any fuel, coolant, or acids that may have accumulated in the oil. The unit does not affect the functional additives of the lube oil. The lube oil is circulated out of the system and through the purifier. The purified lube oil is then returned to the engine's lube oil system. Many operators have found that use of lube oil purification units has significantly reduced the need for lube oil changes, waste lube oil management, and concurrently, the cost of replacement lube oil. Also, a new engine that has been fitted with a lube oil purification unit will break in better and operate more efficiently over time, in part because bearing surfaces and piston rings seat better due to the polishing by particles less than 1 micron in size.
Process or Procedural Modifications
- Slim Holes - The drilling industry has improved the technology of "slim hole" drilling over the past few years. Slim hole drilling should be considered when planning a drilling project. If feasible and used, slim hole drilling reduces the volume of waste drilling fluid and the volume of drill cuttings. The total cost of a slim hole drilling operation may be considerably less than for conventional hole sizes due to the reduced fluid system and waste management costs. Also, smaller casing is required, which may help reduce the total cost of the operation.
- Solids Control for the Drilling Fluid System - An effective way to reduce the volume of drilling fluid waste is the use of solids control. The efficient use of solids control equipment (e.g., hydrocyclones and centrifuges) in combination with chemical flocculants minimizes the need for makeup water to dilute the fluid system. An enhanced solids control system designed to complement a specific drilling operation is a very effective waste minimization technique that can save money.
- Material Balance and Mud System Monitoring - Companies have found that diligent and comprehensive monitoring of drilling fluid properties is effective in reducing the frequency of water and additive additions to the system. Such a system is also referred to as "integrated drilling fluids management." Monitoring devices at various points in the system allow the operator to immediately identify unwanted changes in the drilling fluid system and make the necessary corrections. This technique, in addition to the solids control described above can significantly reduce the costs of the drilling fluid system and the volume of drilling waste remaining at the end of the operation.
- Closed-Loop Drilling Fluid Systems - Closed-loop drilling fluid systems provide many advantages over conventional earthen reserve pits. Closed-loop drilling fluid systems use a series of steel tanks that contain all drilling fluid and equipment used to remove cuttings. These systems enhance the operator's ability to monitor fluid levels and characteristics. The result is more efficient use of the drilling fluid and less drilling waste remaining at the end of the operation. Also, the operator may more easily recycle the waste drilling fluid (also see "Recycling"). Even though it is not always cost effective, some companies have elected to use only closed-loop drilling fluid systems in their operations. However, other companies, such as the one featured in the case history on page 9, have found that use of this system is cost-effective under certain circumstances. Regardless, whenever a closed-loop system is used, the operator reduces his potential future liability associated with a conventional earthen pit and the waste management and site closure costs. It's also good for the company image and public relations.
- Mud Runoff from Pulled Drill String - Running drill pipe into and out of the hole can contribute to the volume of waste in the reserve pit. Lost drilling mud and the excess rigwash required for cleaning it from the rig floor can be major contributors and can be minimized. Devices are available that wipe clean the inner diameter of the drill pipe as it is pulled so that the mud does not run onto the rig floor (about 0.4 bbls of mud can be lost per 1,000 feet of pipe pulled). Thus, drilling mud losses and the need for rigwash are reduced.
- Cementing "On-the-Fly" - When conducting cementing operations, a significant volume of unused premixed cement may remain after obtaining returns. Of course, one way to prevent excess cement is careful preplanning. However, service companies now provide systems that mix neat cement and additives on-the-fly. These systems are also referred to as automatic density control systems. The advantage of mixing on-the-fly is that the mixing process can be stopped as soon as the cementing job is complete. Also, the mixing system can be shut down if the cementing job is interrupted for some reason, thus saving the generation of a much larger volume of unusable premixed cement. The only unused cement mixture is that remaining in the mixing system. The unused neat cement and additives are not wastes and can be returned to the service company for use in the next cementing job.
- Rig Wash Hoses - A simple way to minimize the volume of waste rigwash is to use high-pressure/low-volume nozzles on the rigwash hose. A rigwash hose left running can contribute significantly to the volume of waste in a reserve pit and the water needs for the drilling operation. If feasible, collection and treatment of rigwash for reuse is a good waste minimization technique.
- Drilling Fluid Systems - Improved design and operation of drilling fluid systems can also reduce the need for water. Waste minimization opportunities, such as solids control and detailed system monitoring, have been proven effective in reducing the amount of makeup water needed in a drilling operation (see Process or Procedural Modifications above).
- Dewatering Waste Drilling Fluids - An operator can reclaim water from waste drilling fluids by using mechanical or chemical separation techniques. Large bowl centrifuges, hydrocyclones, and/or chemical flocculants may be used to dewater waste drilling fluids. The reclaimed water may then be reused, thus reducing the demand on, and cost of, new water sources. Proper application of dewatering can result in a reduction of the volume of drilling waste to be managed, thus saving waste management costs, easing site closure concerns and costs, and reducing future potential liability concerns.
Good Housekeeping and Preventative Maintenance
- Drill Site Construction and Rigging-Up - Drill site construction and rigging-up involve the use of heavy equipment, such as bulldozers. Heavy equipment should be well maintained to reduce the potential for fuel and lubricating oil leaks that may contaminate the site. Preventative maintenance and good housekeeping during the construction phase can help prevent the generation of contaminated soil and water. For example, secondary containment beneath fuel storage drums can prevent releases to soil and water.
- Drip Pans and Other Types of Containment - Tanks, containers, pumps, and engines all have the tendency to leak. A good housekeeping practice that can help reduce the amount of soil and water contamination that an operator has to remediate is installing containment devices. Even though a small investment is required, containment devices save money and regulatory compliance concerns in the long run. Also, they can capture valuable released chemicals that can be recovered and used. Some examples of containment include: drip pans beneath lubricating oil systems on engines; containment vessels beneath fuel and chemical storage tanks/containers; drip pans beneath the drum and container storage area; and containment, such as a half-drum or bucket beneath chemical pumps and system valves/connections. Numerous companies have implemented good housekeeping programs to reduce the amount of crude oil, chemicals, products, and wastes that reach the soil or water. These companies have found these programs to be cost effective in the long run (i.e., less lost chemical and product plus reduced cleanup costs). Also, their regulatory compliance concerns and potential future liability concerns are reduced.
- Preventive Maintenance - The companion of good housekeeping is preventive maintenance. Regularly scheduled preventive maintenance on equipment, pumps, piping systems and valves, and engines will minimize the occurrence of leaks and releases of chemicals and other materials to containment systems, or if there are no containment systems, to the environment. Numerous companies have implemented preventive maintenance programs and found them to be quite successful. The programs have resulted in more efficient operations, reduced regulatory compliance concerns, reduced waste management costs, and reduced soil and/or ground water cleanup costs.
- Chemical and Materials Storage - Another important aspect of good housekeeping is the proper storage of chemicals and materials. Chemicals and materials should be stored such that they are not in contact with the ground (e.g., on wooden pallets). Preferably, the raised storage area will include secondary containment and be protected from weather. All drums and containers should be kept closed except when in use. It is very important that all chemical and material containers always be properly labeled so that their contents may be identified at any time. Also, material data safety sheets (MSDSs) and other manufacturer information should be kept on file for all stored chemicals and materials. The use of bulk storage, rather than 55-gallon drums or smaller containers is a preferable way to store chemicals and materials. Proper storage and labeling of containers allows quick and easy identification and classification of released chemical or material in the event of a leak or rupture. In some instances, that could save hundreds of dollars in soil sampling and laboratory analysis costs.
Inventory control is one of the most effective ways to reduce waste generation, regulatory compliance concerns and operating costs. Especially, when combined with proper chemical and materials storage. An inventory control system is easy to implement, especially with the use of computer programs now available. An operator who tracks his chemicals and materials can use them more efficiently and reduce the volume of unusable chemical that must be managed as waste. (Note: Commercial chemical products that are returned to a vendor or manufacturer for reclamation or recycling are not solid wastes. Therefore, it is to the operator's advantage to require vendors to take back empty and partially filled containers for reclamation or reuse.)
Selection of Contractors
Operators should choose contractors who recognize the value of waste minimization and make efforts to apply it in their service. The operator may consider inspecting the drilling rigs being considered for contract to appraise the general condition of the rigs. The contractor should be instructed to minimize maintenance operations on the drilling location (e.g., sand blasting and painting). Any oil and gas waste generated at the operator's drill site is the operator's regulatory responsibility. Therefore, an operator who uses contractors who practice waste minimization can expect reduced waste management concerns, reduced regulatory compliance concerns, and reduced operating costs. The drilling contractor may be instrumental in implementing the waste minimization opportunities discussed above.
The next preferred waste management option is recycling. Recycling is becoming a big business and more recycling options are available every day The following discussion offers some tips on recycling drilling wastes.
- Drilling Fluids - Drilling fluids comprise the largest waste stream associated with a drilling operation. The cost of closing a drilling site is increased if waste drilling fluid in a reserve pit must be dewatered and/or stabilized prior to closure. A better alternative is to recycle or reuse the waste drilling fluid. If feasible, reuse the waste drilling fluid in another drilling project. One company designed a multi-well drilling project where the same drilling fluid was used for drilling each successive well. The result was significant cost savings and greatly reduced waste management concerns. If reuse within your company is not feasible, there are several companies in Texas who take waste drilling fluids for reconditioning and reuse. Another cost effective alternative for reuse of waste drilling fluid is in plugging or spudding of other wells.
- Reserve Pit Water - A drilling operation should consider reclaiming water from the reserve pit by using a dewatering technique. The reclaimed water can then be used as rigwash water, makeup water for the drilling fluid system, and other rig water usage. Additionally, collected stormwater runoff may be suitable for use. This technique can reduce the need for fresh water, and save money.
- Paint Solvent Reuse - A simple technique for reducing the volume of organic paint solvents is to reuse it in stages. An organic solvent, such as toluene, may be used for cleaning painting equipment, but eventually it will become spent and ineffective. The "spent" solvent is not a waste if it is used for another intended purpose. A solvent spent from cleaning painting equipment is still suitable for use in thinning paint. This simple technique can greatly reduce the volume of waste paint solvent that may be subject to stringent hazardous waste regulation.
- Commercial Chemical Products - An operator should implement procedures that recycle any unused chemical products. Whenever a vendor is contracted to supply chemicals, the vendor should be required to take contractual responsibility for unused chemical products and the containers in which they were delivered. As noted under the source reduction opportunity, "Inventory Control," commercial chemical products that are returned for reclamation or recycling are not solid wastes. An operator that manages chemical products properly will avoid the unnecessary generation of unused chemical that must be disposed of. In many instances, those chemical wastes would be hazardous and subject to stringent regulation.
The RRC's Waste Minimization Program can help operators identify recycling options. More information on Waste Minimization Program assistance is presented on page 12. The Texas Commission on Environmental Quality (TCEQ) publishes two useful documents: Recycle Texas and RENEW.Recycle Texas is a listing of many of the companies that take various wastes for recycling. Those wastes include many that are typical of oil and gas operations. RENEW is a waste exchange that is published quarterly. RENEW lists companies that have generated wastes and are making them available for recycling, and RENEW also lists companies that want certain wastes for recycling. Recycle Texas and RENEW are available free of charge from TCEQ and can be obtained by calling 1-800-648-3927.
Training is probably one of the best waste minimization opportunities. An operator's efforts to minimize waste and gain the associated benefits will only be effective if the people in the field understand waste classification and the concept of waste minimization. Also, people in the field should be empowered to implement waste minimization techniques as they are identified. Waste minimization training is becoming more common. Oil and gas associations have begun publicizing waste minimization successes, and technical societies such as the SPE, are publishing more and more papers on effective waste minimization techniques.
RRC Waste Minimization in the Oil Field Manual
Waste Minimization in the Oil Field: This manual, developed with the assistance of the oil and gas industry, offers source reduction and recycling (i.e., waste minimization) concepts, cost effective and practical examples of source reduction and recycling opportunities in the oil field, and information on how to develop an individualized waste minimization plan. The manual also presents a discussion on how to identify hazardous and nonhazardous oil and gas wastes as defined by EPA regulations under the Resource Conservation and Recovery Act.