WASTE MINIMIZATION AT THE DRILL SITE REDUCES ENVIRONMENTAL COSTS

William Thomas Ballantine Newpark Resources Inc. Metairie, La.

In drilling operations, an environmentally managed, multiple pit system can reduce the costs of waste cleanup and disposal and ultimately limit the operator's liability.

For a new drilling location, the operator should first perform a native-soil test and an environmental assessment. An historical background check in the assessment may discover if a well has been drilled on this location previously. If so, a buried pit or other environmental problem may exist on location.

The native-soil test gives the operator a background "signature" for the location and, therefore, a benchmark to indicate the point at which to stop cleanup operations. The native-soil test also serves as a guideline for the restoration project after the well has been drilled.

In developing the well plan and the audit, the operator should give due consideration to all chemicals and fuels handled and, most importantly, their ultimate disposal. A waste minimization program actually begins during the well planning.

The chronological progression of the drilling of the well should dictate how the generated waste is managed (Fig. 1). Fig. 2 shows the relative environmental costs on a typical drilling location.

Use of a multiple pit system, rather than a single pit, can considerably reduce the amount of waste for disposal. The casing program designed during well planning will then help predict the volumes and types of wastes generated. Then a waste management program can be organized to establish handling procedures.

The top-hole material can be segregated in one pit and later spread around the location. The top-hole material is native soil and, if not later contaminated with material from deeper in the well, can be treated on location.

As drilling progresses, saltwater, weight-up material, kick fluids, and bottom hole fluids can be handled in various pits and treated specifically. Fluid segregation minimizes the waste and disposal costs.

If all the material is put in one large pit, the entire volume becomes waste that must be handled for disposal in some manner. If any one fluid is contaminated, then, according to the U.S. Environmental Protection Agency (EPA), the entire pit volume is considered contaminated and must be handled as such.

During drilling operations, the liquids generated can be separated and pumped back downhole where they originated, thereby limiting the operator's cost and liability.

When purchasing a property, an operator should conduct an environmental assessment to identify possible environmental problems. These problems can quite often be identified and quantified and can become part of the purchase package.

Ultimately, the existing problems are the responsibility of the initial generator. The operator acquiring the property, however, must remain aware of a potential environmental problem by addressing it during the purchase rather than later during litigation.

For cleanup of drilling pits or old production pits, a thorough assessment should identify the extent of contamination, the location of the clay liners, and the boundaries of the waste. These boundaries, once determined, should not be violated because the pit contamination could spread and enlarge the contamination area.

If haul off and disposal are required, the crew should use as little wash water as possible during cleanup of the containers. The operator should audit the transporter and disposal facilities to determine their capabilities in minimizing the wash water.

If the pit sludge or drilling mud is transported in a shale barge, the barge will eventually have to be cleaned for return. (The barge can be cleaned with 1,000 bbl of water or prudently with 200 bbl.) This wash water becomes waste and requires proper disposal.

AUDITS

It is a good idea for an operator to audit the disposal facilities, the receiving and transfer stations, and the transporter to guarantee proper waste handling. The operator should follow and track its waste from "cradle to grave," that is, from the point of generation to the point of disposal.

The audit should include permit checks to ensure they are adequate and current. The operator should check with the permit issuing authority for outstanding compliance orders or other problems.

The audit should definitely include on site physical inspections, including interviews with the personnel responsible for the specific operations related to the operator's waste.

Most oil companies and their environmental consultants have detailed audit forms that provide for a formal, orderly audit. Quite often, the audited company must first complete a questionnaire to lay the groundwork for the on site review.

STORM WATER

Of particular interest lately are the regulations on handling storm water runoff, as related to the National Pollutant Discharge Elimination System waste water permitting program by the EPA.

Following a heavy rain, oil and chemicals from the location may contaminate an entire area or local streams. The EPA has therefore dictated that operators must have a permit stating what materials might run off a location during a storm.

Proper handling of storm water, by use of ring levees and containing flow, can help reduce the volume of waste for disposal.

RCRA

Operators must diligently monitor regulations and proposed legislation, especially the Resource Conservation and Recovery Act (RCRA). The U.S. Congress has been reviewing the amendments to the RCRA and has indicated there will be no change. The EPA supports the exempted wastes and the primacy of the individual states in this area. Furthermore, President Clinton has stated to the industry that he would not support any changes to the current exemptions.

Nonetheless, it is industry's responsibility to stay abreast of potential changes in regulations.

The amendments to RCRA exempt oil field exploration and production wastes from the hazardous waste requirements. If this exemption is removed, the environmental costs for the domestic oil and gas industry would increase dramatically, possibly shutting down many fields and wells.

The API projected that hazardous waste regulation under RCRA could cost the petroleum industry approximately $44 billion initially and $5 billion annually and force the premature abandonment of 150,000 wells.

MANAGED PIT SYSTEM

Onshore drilling sites have traditionally used a single large reserve pit to contain drilling waste cuttings, water, and other liquids. Increased environmental awareness and responsibility, landowner concerns, and the complication of greater drilling depths can make the traditional reserve pit extremely expensive, if not prohibitive, to operate.

An environmentally managed reserve pit system can minimize the waste and, therefore, the cost of drilling waste disposal. The reserve pit system is built with four or more pits. The drilling wastes are separated into different pits to keep uncontaminated wastes from the more-contaminated wastes. (Less-contaminated wastes are generally less expensive to dispose of.)

The managed pit system minimizes or eliminates off site disposal and maximizes the use of the traditional on site disposal methods: land farming, burial, and injection. The most effective application of this system is when the drilling waste can be land farmed or injected on site. Experience has also shown that proper use of a managed pit system can also result in savings when much of the waste is handled off site (Table 1).

ADVANTAGES

The two main advantages of the managed reserve pit system are the ability to process drilling wastes as they are generated and the isolation of wastes to minimize contamination. These advantages are reflected in lower disposal costs.

The ability to process drilling waste as it is generated is significant because the volume available for contamination is reduced. In a conventional reserve pit, the entire pit contents could be contaminated.
Immediate processing of wastes reduces the impact of unexpected problems, and the rig personnel become more aware of the effects of their actions on waste management.
The ability to isolate waste is beneficial because it prevents small amounts of highly contaminated waste from affecting large amounts of manageable waste. Isolating wastes also allows flexibility in the scheduling of waste processing. Isolation provides the opportunity for selected waste to be treated by alternative methods such as solidification or dewatering.

DESIGN

A successful environmentally managed reserve pit program must begin with a design meeting. The meeting should include operator representatives (drilling foremen, operations engineers, landmen, and environmental personnel), site preparation contractors, reserve pit management personnel, and all third-party personnel.

The topics should include the well drilling program, location orientation, position of the well stake, available acreage adjacent to the site for land farming, landowner concerns, regulatory limitations, choice of drilling contractor and service companies, and accessibility to the drill site.

The next step in the design program is site assessment. The assessment should include photographing the site, sampling and testing background soil, establishing good communications with the landowner and determining the runoff areas and other pertinent land conditions.

Background soil testing is highly recommended to determine the possibility of existing contaminants in the soil and to establish soil characteristics that may affect land farming operations.
Good communications with the landowner can answer many questions about how the area handled rainwater runoff and land use prior to and after drilling.

A checklist should be made to help assemble the data for the reserve pit design. The reserve pit system is then designed to handle the volumes of waste to be generated, the expected weather conditions, and the planned disposal of the drilling wastes. Additionally, the pit system can then be properly oriented on the planned drill site.

The envirornmentally managed reserve pit system is predicated on two primary operational considerations:

The ability to land farm uncontaminated material on site
Annular disposal of contaminated material downhole.

Land farming operations for a reserve pit management project require an additional 4-5 acres of land in addition to the actual drill and pit site. This area is necessary because the solids should be spread to a maximum thickness of 3 in. Amounts greater than 3 in. will not dewater and dry properly, making land farming and dilution difficult.

Annular disposal requires approval from the appropriate regulatory agency and is affected by casing depths, cement requirements, and underground sources of drinking water.

Fig. 3 shows a typical multiple pit location. The managed pit system can accommodate most locations by allowing for different configurations, orientation, number and size of pits, well depths, and drilling mud programs.

OPERATION

In daily operation of the environmentally managed reserve pit system, Pit 1 is the shaker pit (Fig. 4). The solids control equipment discharges waste into this pit. Material in this pit may be moved by dragline to Pit 2 for storage or directly to the land farming area. Fluid can be transferred from Pit 1 to Pit 3 through a pipe set in the levee wall or by centrifugal pump.

The fluid in Pit 3 is stored to allow the solids to settle. The water is then moved by centrifugal pump to Pit 4.

The water in Pit 4 is either recycled for rig use or tested and treated for discharge as allowed by regulations and an appropriate permit. Rainwater and waste water from the location may be pumped directly to Pit 3.

Pit 5 is an emergency pit for fluids from saltwater flows, kicks, and cement overruns.

Maintaining freeboard (maximum allowed volume in the pit system) by treating and discharging water can be expensive depending on the duration of the drilling operations. The drilling program should therefore include a water conservation program, which includes the following:

Construction of a location no larger than necessary
Use of automatic shutoff nozzles on all hoses on the rig floor and washdown racks
Recycling of reserve pit water to wash out slides draining to the shaker pits
Use of ring levee water (if acceptable) for makeup water
Use of a drip pan beneath rig floor with flexible hoses draining to the cellar to avoid dirty water and mud dripping on the rig substructure and location
Installation of water meters on freshwater sources to monitor and control water use.

PIT MONITORING

The reserve-pit management personnel must daily monitor the environmentally managed reserve pit program. The personnel survey the system daily to determine volumes in each pit, changes from the previous day, work performed in handling wastes from any of the pits, rainfall amounts, and weather conditions.

This information is charted daily on the work progress report and provides documentation on waste volumes handled and disposal methods throughout the job.

Samples can be extracted from the pit system and analyzed by an approved laboratory according to current state rules and regulations. The sample analyses dictate the disposal method used.

Open communication between the reserve pit management personnel, mud company personnel, drilling contractor, and the company representatives is important and should be stressed during the spud meeting. All parties must know complete daily activity and also what is planned for the following day.

WASTE MANAGEMENT

Reserve pit management is based on handling drilling waste by on site disposal methods.

The program uses traditional on site disposal techniques, including land farming mud and cuttings which meet regulatory guidelines for on site disposal, burial, treatment and discharge of pit water and rainwater, and injection.

If the on site disposal methods cannot be used, off site disposal of the contaminated material at an approved commercial disposal facility may be necessary. Off site disposal is the last option considered because of the greater costs compared to on site disposal.

Land-farming operations consist of isolating mud and cuttings and then spreading the material no greater than 3-in. thick, allowing the material to dewater, then plowing the solids into the existing ground to an appropriate depth for proper dilution.

Adding soil and replowing are acceptable in land farming.

Pit water is treated and discharged when the treating pit becomes full. Pit water samples are analyzed according to current regulations to determine the level of contamination. The water is chemically treated to reduce contaminants to within regulatory limits, analyzed again, and finally discharged on site after regulatory approval is obtained.

Pit waste that cannot be land farmed or chemically treated and discharged is stored in the reserve pit system for annular disposal. The pit waste is physically mixed into a slurry by the dragline and then fed to a disposal pump unit which screens out the larger solids and injects the material. Chart recorders monitor pump pressures, time, and disposal volumes.

Any residue in the pit system after annular injection may require off site disposal. Relatively dry material can be loaded into dump trucks, but wet material will have to be loaded into vacuum trucks. An approved commercial transporter must haul the material to an approved commercial disposal facility.

CLEANUP

Once drilling operations are complete and the wastes have been disposed of on site or off site, the reserve pit system can be backfilled with the earthen levee material.

Trash and debris must be removed from the site and properly disposed of. The pit system area is leveled and restored to predrilling conditions.

Post-closure sampling and analyses are performed on the backfilled area to ensure compliance with relevant regulations.

All documentation is compiled into a post-closure package for the well files. These documents are helpful later in filling out forms concerning the disposition of the waste.

ZERO DISCHARGE

Sometimes an environmentally managed pit system cannot be used, mainly because of physical constraints on locations Zerodischarge or closed-loop systems can then be used to reduce the amount of waste generated. Fig. 5 shows a well requiring zero-discharge operations because the surrounding marshlands were not suitable for pit construction.

These systems use highspeed shakers, centrifuges, and batch treatment to separate the cuttings, solids, and fines out of the mud system. The remaining fluid is recycled to the active mud system.

Depending on the well plan, these systems can be very effective in minimizing the amount of waste generated.

The generated waste should then be managed and sent to a permitted disposal facility.

Table I roughly compares the cost of zero discharge to an environmentally managed pit system.

In this cost analysis, the managed pit system, even with 30,000 bbl of waste hauled off, is less expensive than a comparable zero-discharge operation.