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1 Drilling, Completion and Workover Fluids 2008. Special Supplement to Published in June 2008. Copyright 2008 Gulf Publishing Co. All rights reserved. For additional copies, contact Gulf Publishing Company. Telephone: 713-529-4301 Fax: WORLD OIL, Gulf Publishing Co., Attention: Reprint Department, Fax No. 713-520-4433. Mailing Address: Gulf Publishing Co., Box 2608, Houston, TX 77252 USA. WORLD OIL'S. FLUIDS 2008. Classifications of fluid systems Descriptions of fluid-system classi- anhydrite contamination but are sus- sulate drill solids or to extend bentonite fications, product functions and source ceptible to gelation and solidification at clay in a low-solids mud.

2 Companies are listed on these pages. Sys- high temperatures. tem descriptions and product definitions Saltwater systems. Several mud sys- have been kept as simple as possible and, High-performance water-based tems are included in this classification. wherever practical, they reflect general muds (HPWBM). These are usually re- Saturated salt systems are used to drill salt industry practice and terminology con- formulated polymer systems containing formations. Lower levels are usually re- sistent with descriptions adopted by the system-specific products to deliver shale ferred to as brackish or seawater systems.

3 American Petroleum Institute (API) and stability, clay and cuttings inhibition, Saltwater muds are usually prepared the International Association of Drilling lubricity and high ROP, while minimiz- from brackish, seawater or produced- Contractors (IADC). ing bit balling/accretion and downhole water sources and dry sodium chloride torque problems. Some HPWBM use (or other salts, such as potassium chlo- WATER-BASED SYSTEMS borehole stabilizing products to reduce ride used for shale inhibition), are added pore pressure transmission similar to to achieve desired salinity. Various spe- Non-dispersed.

4 These systems include oil-based muds. Therefore, HPWBM cialty products, such as attapulgite, car- spud muds, natural muds and other are suitable to use whenever environ- boxymethyl cellulose (CMC), starch and lightly treated systems that are generally mental liabilities and associated waste others, are used to increase viscosity for used for shallow wells or top-hole drill- management costs limit the application hole-cleaning properties and to reduce ing. Thinners and dispersants are not of OBM/SBM. fluid loss. added to disperse drill solids and clay particles. Low solids. Listings include systems in OIL-BASED MUD SYSTEMS.

5 Which the amount (volume) and type of Oil-based systems are used in vari- Dispersed. At greater depths, where solids are controlled. Total solids should ous applications, where fluid stabil- higher densities are required, or where not range higher than about 6% to 10% ity and inhibition are necessary, such as hole conditions may be problematic, by volume. Clay solids should be some high-temperature wells, deep holes, and muds are often dispersed, typically with 3% or less and exhibit a ratio of drilled where sticking and hole stabilization are lignosulfonates, lignites or tannins. solids to bentonite of less than 2:1.

6 Problems. They consist of two types of These and similar products are effec- Low-solids systems typically use poly- systems: tive deflocculants and filtrate reducers. mer additive as a viscosifier or bentonite 1. Invert emulsion muds are water-in-oil Potassium-containing chemicals are extender and are non-dispersed. One emulsions, typically with calcium chloride frequently used to provide greater shale primary advantage of low-solids systems brine as the emulsified phase and oil as the inhibition. Specialized chemicals are is that they significantly improve drill- continuous phase.

7 They may contain as also added to adjust or maintain specific ing penetration rate. much as 50% brine in the liquid phase. mud properties. Invert emulsion muds are a relaxed . Polymer/PA/PHPA. Muds incorporat- emulsion, and have lower electrical sta- Calcium treated. Divalent cations, ing generally long-chain, high-molec- bilities and higher fluid-loss values. Con- such as calcium and magnesium, when ular-weight polymers are used to either centration of additives and brine content/. added to a freshwater drilling mud, in- encapsulate drill solids to prevent disper- salinity are varied to control rheological, hibit formation clay and shale swelling.

8 Sion and coat shales for inhibition, or for filtration and emulsion stability. High levels of soluble calcium are used to increasing viscosity and reducing fluid 2. Oil-based muds are formulated with control sloughing shale and hole enlarge- loss. Various polymers are available for only oil as the liquid phase and are often ment, and to prevent formation damage. these purposes, including cellulose, natu- used as coring fluids. Although these sys- Hydrated lime (calcium hydroxide), ral gum-based products, and acrylamide. tems pick up water from the formation, gypsum (calcium sulfate) and calcium Frequently, inhibiting salts, such as KCl no additional water or brine is added.

9 Chloride are principal ingredients of cal- or NaCl, are used to provide greater shale All oil systems require higher additional cium systems. stability in all of these fluids. These sys- gelling agents for viscosity. Specialized Calcium-treated muds resist salt and tems usually contain a minimum amount oil-based mud additives include: emulsi- of bentonite and may be sensitive to fiers and wetting agents (commonly fatty divalent cations, such as calcium and acids and amine derivatives) for viscos- magnesium. Most polymers have tem- ity; high-molecular-weight soaps; surfac- On The Cover: Completion fluids perature limits below 300 F but, under tants; amine-treated organic materials.

10 Technicians are consulting with a cli- certain conditions, may be used in hotter organo clays and lime for alkalinity. ent on a rig in the North Sea. Photo wells. A special class of water-based muds courtesy of MI-SWACO. use partially hydrolyzed polyacrylamide Completion FLUIDS. (PHPA) as an additive, either to encap- Solids-free and typically formulat- World Oil JUNE 2008 F 105. WORLD OIL'S FLUIDS 2008. Abbreviations of company names ADM Archer Daniels, Midland, Decatur, IL, USA, Croda Croda (form. Uniqema Inc.), New Castle, M&D M&D Industries of Louisiana, Lafayette, DE, USA, LA, USA, AHC Advance Hydrocarbon Corp.