A client recently suggested that I should write about landfarming - the practice of disposing of drilling mud and cuttings by spreading it over land.
Drilling mud is the common term for the fluid used in the process of drilling a well. It is made up of a mixture of clay (bentonite) in a base of either water, diesel or mineral oil. It also contains an organic material such as lignite to stabilize the slurry and a material such as barite to increase its density. The drilling mud is circulated through the wellbore - pumped down the inside of the drill stem, through the drill bit, and up the outside or annulus of the hole as the well is being drilled. The drilling fluid carries the cuttings made by the drill bit back up and out of the hole, and it helps to cool the drill bit. The clay also coats the outside of the open hole to help seal off porous geologic strata. The drilling fluid is circulated through a pit or tank, where the cuttings settle out, and re-injected into the hole. Usually an earthen "reserve pit" is constructed for this purpose.
The actual content of drilling mud varies with conditions in the hole and the formations being drilled. In the Eagle Ford, for example, water-based mud is typically used for the vertical section of the hole, and oil-based mud is used for the horizontal section.
After drilling is completed, the drilling mud and cuttings in the reserve pit must be disposed of. These wastes are exempt from federal regulation, and state regulations vary. Landfarming of water-based mud is a generally accepted method of disposing of the contents of the reserve pit in most states.
In Texas, oil and gas exploration and production is regulated by the Texas Railroad Commission, and its rules regarding disposal of drilling fluids are at 16 Texas Aministrative Code Section 3.8, commonly called Rule 8, or "The Pit Rule." That rule defines "landfarming" as "a waste management practice in which oil and gas wastes are mixed with or applied to the land surface in such a manner that the waste will not migrate off the landfarmed area."
In general, Rule 8 allows wastes remaining in reserve pits to be disposed of either by burial on-site or by landfarming on-site. But the rule requires the consent of the surface owner for landfarming:
RRC Rule 8 (16 TAC, Part 1, Sec. 3.8):
(3) Authorized disposal methods.
(C) Low chloride drilling fluid. A person may, without a permit, dispose of the following oil and gas wastes by landfarming, provided the wastes are disposed of on the same lease where they are generated, and provided the person has the written permission of the surface owner of the tract where landfarming will occur: water base drilling fluids with a chloride concentration of 3,000 milligrams per liter (mg/liter) or less; drill cuttings, sands, and silts obtained while using water base drilling fluids with a chloride concentration of 3,000 mg/liter or less; and wash water used for cleaning drill pipe and other equipment at the well site.
(D) Other drilling fluid. A person may, without a permit, dispose of the following oil and gas wastes by burial, provided the wastes are disposed of at the same well site where they are generated: water base drilling fluid which had a chloride concentration in excess of 3,000 mg/liter but which have been dewatered; drill cuttings, sands, and silts obtained while using oil base drilling fluids or water base drilling fluids with a chloride concentration in excess of 3,000 mg/liter; and those drilling fluids and wastes allowed to be landfarmed without a permit.
First, the RRC does not require a permit for on-lease disposal of water-based drilling fluids. If the waste is to be disposed of by burial, the drilling fluids must be "dewatered" before burial. The rule defines "dewatering" as "to remove free water."
Second, if the operator wants to dispose of water-based drilling mud by landfarming on the lease, it must have the permission of the landowner, and the fluids must have a chloride (salt) content of less than 3,000 mg/l.
There are also commercial landfarming operations that take spent drilling mud and dispose of it for operators. Those operations do require a permit from the RRC, and many such permits have been granted. A list of recent permits can be found here. he RRC has specific requirements for such permits, including testing the soil and the drilling fluid for chloride content and heavy metals. A recent story about a criminal investigation of such a commercial operation raises questions about how well the RRC regulates such sites.
Note that disposal of reserve pit contents by burial does not require consent of the surface owner. Unless the oil and gas lease prohibits disposal by burial, the operator will be able to bury the pit contents over the objection of the surface owner. If the mineral owner also owns the surface estate, the lessee may seek to negotiate the right to landfarm pit contents in the lease itself. If the surface owner does not own any minerals, the operator may offer to compensate the surface owner for the right to landfarm pit contents.
Texas A&M's AgriLife Extension Service has published a good summary of the risks and hazards of landfarming pit wastes, which can be found here. Among A&M's conclusions:
- Oil may be contained in water-based drilling mud, part of the materials produced during the drilling operations. Excess amounts of oil - in excess of 1% of the volume of the waste disposed of - are generally toxic to plants.
- Chlorides (salts) in drilling fluid can be detrimental to soils. Soil is generally considered salt-affected or "saline" when the electrical conductivity of the saturated paste extract exceeds 4 millimhos per centimeter.
- Drilling fluids can also contain boron, arsenic, barium, chromium, copper, lead, nickel and other heavy metals that can be harmful in certain concentrations.
A&M recommends that any agreement to allow landfarming should specify testing protocols for possible harmful elements, both in the soil and in the drilling fluids, by a qualified professional; specification of the proper rate of application, and possibly requirements for application of soil amendments to promote treatment of the waste; requirements for mixing the waste into the soil; and requirements for re-seeding and reclamation when the landfarming is complete, possibly with a required bond to assure performance.