Drilling Fluids

Abstract

Drilling fluids (muds) play a vital role in the drilling of oil and gas wells. These muds are typically complex chemical mixtures formulated to perform a variety of functions under a wide range of down hole temperatures and pressures, but yet are nondamaging to the environment and safe for personnel to handle. These fluids are circulated down the hollow drill string and up the annulus, formed by the drill string and the hole to remove formation material dislodged by the bit. The fluids must have sufficient density to offset formation pressures to prevent a blowout and to maintain a stable well bore, but be formulated to prevent excessive loss of fluid to permeable formations. Other important functions include lubrication of the drill bit and drill string, collection of information about subsurface formations, and noncorrosivity to surface and down hole equipment. Drilling fluids are composed of liquids (water, petroleum oils, and other organic liquids, eg, synthetic brine fluids), dissolved inorganic and organic additives, and suspended, finely divided solids of various types. This article describes drilling fluid classification, properties, materials used as drilling fluid additives, testing, economics, and an update on current environmental restrictions on drilling fluids/muds in the North Sea and in the Gulf of Mexico. A detailed section has been devoted to clear brine drilling fluids (CBFs) that are used in completion and workover operations. Also presented is a selection of new and recent drilling fluid formulations from the patent literature.

Vegetation Response to a One-Time Spent Drilling Mud Application to Semiarid, Mixed-Grass Prairie

“…Drilling muds (or fluids) are used during exploratory and development drilling for oil and natural gas to lubricate and cool the drill bit and control subsurface wellbore pressure (Neff et al 1987;Ukeles and Grinbaum 2004). They also function to remove drilled-out rock cuttings from the well, clean the bit and the bottom of the hole, and stabilize the wellbore.…”

Waste Management during the Production Drilling Stage in the Oil and Gas Sector: A Feasibility Study

“…The drilling mud is selected based on the geological conditions of the producing formation and the physical and chemical properties of the hydrocarbons [14]. Drilling muds are classified into aqueous (highly colloidal clay or polymer muds), oil (diesel fuel or crude oil), pneumatic (compressed dry air, natural gas, aerosol, or foamed gas) and synthetic (vegetable esters, olefins, linear paraffins, simple esters, or acetals) [15][16][17][18]. The buffer fluid is similar in composition to the drilling mud and is intended for cleaning the wellbore before plugging it [19].…”

“…The composition of the drilling mud includes a large number of reagents ensuring specific properties (density maintenance, rheological, thermal, and other properties): moisture and viscosity reducers, clay dispersion inhibitors, thermostabilizing agents, Ca 2+ and Mg 2+ binding ions, lubricants, emulsifiers, defoamers, pH regulators, H 2 S absorbers, fillers, etc. [15]. While some additives may not be inherently toxic, their interaction with formation minerals can yield poisonous substances, exemplified by the formation of harmful components when barite interacts with carbonates and chlorides.…”

“…While some additives may not be inherently toxic, their interaction with formation minerals can yield poisonous substances, exemplified by the formation of harmful components when barite interacts with carbonates and chlorides. In addition to barium salts, heavy metals present in bentonite clays, such as lead, copper, zinc, nickel, cadmium, cobalt, antimony, tin, bismuth, and mercury [15], as well as silver, tungsten, iron, gold, and manganese [20], contribute to the toxicity of drilling muds.…”

Surface Application of Oil‐Base Drilling Mud Mixed with Gypsum, Limestone, and Caliche

“…Drilling mud is manufactured and utilized by the drilling industry to help cool the drill bit, maintain borehole pressure, and aid in bringing the drill cuttings to the surface where the fluids and cuttings can then be separated (Ukeles and Grinbaum, 2004). Drilling muds are comprised of a base liquid (water or diesel fuel) with other potential additives such as barium sulfate, bentonite, calcium hydroxide, and byproducts such as cotton ( Gossypium hirsutum L.) seed hulls, used for specific drilling conditions (Moseley, 1983).…”