Section Seven
OILFIELD AND GAS PIPELINE WASTES
57    DELIQUIFICATION OF OILFIELD DRILLING SLURRIES
AND PRODUCTION SLUDGES
Stephen D. Field, Assistant Professor
Department of Civil Engineering
Andrzej Wojtanowicz, Assistant Professor
Department of Petroleum Engineering
Kevin Cange, Graduate Research Assistant
Department of Civil Engineering
Louisiana State University
Baton Rouge, LA 70803
INTRODUCTION
Recent concern over the past improper disposal of liquid and solid wastes has led to the creation of
several regulatory systems to assure proper waste management. Although waste drilling fluids associated with the exploration and production of oil and natural gas are not classified as hazardous wastes,
the potential for mismanagement of the waste drilling fluids exists. Waste drilling slurries (muds) and
production sludges from exploration and production activities have typically been discharged into
earthen surface impoundments, or pits. The waste drilling fluids consist of drilling mud(s), borehole
cuttings, and various other wastes generated at the drill site [1]. Consequently.the pits may contain a
variety of materials, including heavy metals, crude oils, diesel oils, high salt concentrations, and
bentonite (mud) suspensions.
Regulations have been developed by the State of Louisiana requiring proper storage, treatment, and
disposal of waste drilling fluids. Because of the large number of pits in existence (over 10,000 in
Louisiana), volume reduction is of critical concern. This paper presents results of chemical conditioning, vacuum filtration, and pressure filtration techniques for deliquifying water-base and oil-base
drilling muds and production sludges.
Reserve Pits
The majority of on-shore oil and gas exploration and production wells in Louisiana are drilled using
water-base muds. Water-base muds are colloidal suspensions of low quality clays, bentonite, and
water, and commonly are used for shallowwell drilling. These muds may contain a variety of additives
to improve the required characteristics for drilling purposes. Bariic, or barium sulfate, is used as a
weighting agent to increase the density of the mud. Increasing the density of the mud serves to keep
borehole cuttings from settling in the mud. Lignite and chrome-lignosulfonates are used as thinners.
A variety of corrosion inhibitors may also be used in the muds including sodium hydroxide and zinc
carbonate. In addition to these and other additives, materials such as lead from pipe dope and crude
and diesel lubricating oils may be unintentional constituents of the water-base muds.
During surface drilling, water is added to control the mud viscosity, which dilutes the drilling mud,
resulting in excess volumes. The mud, along with cuttings removed from the mud via shaker screens,
hydrocyclones and centrifuges for desanding and desilting, and mud cleaning , traditionally have been
disposed in reserve pits. This mud and associated cuttings are non-toxic and could be returned to the
environment in many cases with minimum management practices such as neutralization (if required)
and land spreading (dispersing).
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