Using Minimum Pit and Zero Cost in Drilling Operation – Environmental Protection

shale shaker image

The Drilling, Health Safety Environmental and Location Construction departments would work together, a division of Oiltools international, to apply new technology to continuously improve and achieve “reduced pit drilling” to minimize the environmental impact.

The intention was to achieve these environmental goals with the costs offset by cost reductions. The project is being implemented in several stages:

  • Redesign the location for improved drainage, and process the water base mud and rainfall.
  • Maximize the recovery of synthetic oil base mud to minimize the oil content in cutting.
  • Re-green the remediated soil with a variety of vegetables and fruits.

Methodology and field activities for recover the liquid phase

Liquid waste is divided into two categories:

  1. Liquid waste or cuttings from the drilling fluid. This liquid is processed using water clarification after the drilling in the surface section is completed.
  2. Liquid from location drainage and rainfall. This liquid is collected into the catch pit and treated using water clarification during the drilling operation.

Solids Control Equipment

High speed, high G-force shale shakers are used to maximize liquid recovery while the drilling operation is in progress. Rainwater and location drainage is treated continuously while drilling and to process the water base mud after finished the surface section drilling operation.

layout solids control for minimum pits
Figure 1 shows the process used
 solids control system layout location design to accommodate the rainwater.
Figure 2 shows the location design to accommodate the

Environmental Regulations

Before starting the drilling operation, water samples are collected from the environment or “body water”, and tested. During clarification process, samples are tested to monitor the environmental impact. Particular attention is paid to the discharge water from the process.

The regulations cover three types of water quality, depending on the discharge environment. Type “B” is for drinking water, type “C” for fishponds, and type “D” is for agriculture areas. The discharge water is tested for toxicity (LC-50), due to the number of fishponds around Vico’s drilling locations. And, solid waste from the water base mud is tested for heavy metals using toxicity characteristic leaching procedures.

Methodology and field activities for processing oil and cutting from synthetic oil base mud

High speed, high G-force shale shakers and centrifuges are used to maximize the recovery of synthetic oil base mud. This equipment reduces the oil in the cuttings from 20-25% by weight to 8-12% by weight by recovering 35- 40 barrels of oil base mud per 1000 feet drilled.

 high G-force shale shaker
High G-force shale shaker

The oil cuttings will be treated using land farming bioremediation. This method uses aerobic microbes to degrade or breakdown toxic hydrocarbons to the harmless end products carbon dioxide, water, and biomass. The microbes, surfactants and nutrients are applied to the surface of the waste and mixed with the aerobic layer of topsoil.

The soil is kept moist by watering if necessary and plowed every three days or a week to provide oxygen. This system was previously successful in reclaiming a site used for a diesel-based mud plant, which was a more severe test of the methodology.

In bioremediation, hydrocarbon degrading microbes use organic matter as their source of food and energy. The source may be raw crude oil or refined product such as diesel, gasoline or lube oil. The microbes digest the hydrocarbon and break them down into the harmless end product carbon dioxide and water, with the chemical formula.

C7H8 + 9O2 => 7CO2 + 4H2O

Increasing the oxygen will increase the rate of biodegradation.

Methodology for re-vegetation of contaminated soil

PERTAMINA / Vico chose a number of common vegetables and fruits to be planted. The criteria to select the plants were as follows:

  1. Vegetables and fruits consumed by the local people.
  2. Easy growth.
  3. Crops can be harvested within six months.
  4. The seeds or seedling are commonly available.
  5. Crops are easy to maintain.

Based on the above we chose tomatoes, marrow, eggplant and cucumber. The leaves, fruits, and root of these plants were analyzed to determine if there was any contamination from the waste oil base mud.


Drilling location

In the past, drilling operation typically used a large location with a water base mud for drilling the surface hole and a synthetic oil base mud for drilling the production section. All waste from the operation was dumped into a large pit with approximately 2400 m2 surface area. By building the locations to channel the rainwater to a holding area, the mud pit was reduced by 22%.

“Reduced pit drilling” has been achieved. On subsequent locations, mud pits were reduced 25%, 50% and 80% to a single 420 m2 pit which is used to collect oil base mud cutting before remediation. Once the system and waste disposal is proven, pitless drilling will be initiated.

Mud pit reduction process in closed loop system
Figure 3 shows the progress for reducing the mud pits.
As shown, the reduction was made in 3 wells over a 4
month period.

The bioremediation is still in a trial stage. Depending on the success, the requirement for other technologies such as thermal desorption will be evaluated.


  1. Cost for drilling waste handling equipment was USD 94,000 per well:
    • Liquid phase clarification was USD 71,000 per well, including support equipment and engineers.
    • G-force shale shaker to recover oil and reduce oil content was USD 13,000 per well, including the engineer.
    • Land farming bioremediation was USD 10,000 per well.
  2. Cost saving was USD 95,000 per well:
    • Land saving by reducing 80 % area of mud pit was USD 55,000 per well.
    • Oil recovery cost from G-force shale shaker was USD 40,000 per well.


Liquid waste and water base mud processing
  • The clean water from the water base mud, location drainage, and rainfall processed can be recycled for the rig operation or disposed to the environment.
Oil and cutting from oil base mud
  • Oil base recovered from the G-force shale shaker was approximately 35-40 barrels per 1000 feet of 8-1/2” hole drilled.
  • Oily cuttings were reclaimed using landfarming bioremediation.
  • The oily contaminated soil was cleaned-up from an initial average oil content of over 8.0 % oil by weight to soil that contained less than 0.5% oil by weight.
  • Bioremediation conserves natural resources.
Re-vegetation of contaminated soil.
  • The remediated soil was successfully planted with a variety of mixed vegetables and fruits. The leaves, fruits and roots af these plants were analyzed to verify that there was no contamination from the waste oil base mud.
Drilling location
  • The mud pit was successfully reduced by 80% from 2400 m2 to 420 m2.
  • Zero cost in the environmental protection in drilling operation was achieved, as the increased cost be offset by cost reductions.
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