Fluid loss control

Polyacrylamides are used in many other oilfield appUcations. These include cement additives for fluid loss control in well cementing operations (127), viscosity control additives for drilling muds (128), and fracturing fluids (129). Copolymers [40623-73-2] of acrylamide and acrylamidomethylpropanesulfonic acid do not degrade with the high concentrations of acids used in acid fracturing. 

Brine-polymer systems are composed of water-salt solutions with polymers added as viscosifers or filtration control agents. If fluid loss control is desired, bridging material must be added to build a stable, low permeability bridge that will prevent colloidal partial movement into the formation. 

Starch is also used for fluid loss control. It does not provide carrying capacity therefore other polymers are required. Although starch is relatively cheap, it has two serious limitations (1) starch is subject to fermentation, and (2) it causes significant permeability reduction due to plugging. 

The damage of the formation resulting from the use of a filtration loss agent can be a serious problem for certain fields of application. Providing effective fluid loss control without damaging formation permeability in completion operations has been a prime requirement for an ideal fluid loss control pill. 

Filter-cakes are hard to remove and thus can cause considerable formation damage. Cakes with very low permeability can be broken up by reverse flow. No high-pressure spike occurs during the removal of the filter-cake. Typically a high-pressure spike indicates damage to the formation and wellbore surface because damage typically reduces the overall permeability of the formation. Often formation damage results from the incomplete back-production of viscous, fluid loss control pills, but there may be other reasons. 

Hydroxyethylcellulose with a degree of substitution of 1.1 to 1.6 has been described for fluid loss control in water-based drilling fluids [1473]. An apparent viscosity in water of at least 15 cP should be adjusted to achieve an API fluid loss of less than 50 ml/30 min. Crosslinked hydroxyethylcellulose is suitable for high-permeability formations [344,346]. 

A derivatized hydroxyethylcellulose polymer gel exhibited excellent fluid-loss control over a wide range of conditions in most common completion fluids. This particular grated gel was compatible with the formation material and caused little or no damage to original permeability [1341]. Detailed measurements of fluid loss, injection, and regained permeability were taken to determine the polymer particulate s effectiveness in controlling fluid loss and to assess its ease of removal. Hydroxyethylcellulose can be etherified or esterified with long chain alcohols or esters. An ether bond is more stable in aqueous solution than is an ester bond [96]. 

A fluid loss additive is described that consists of granular starch composition and fine particulate mica [337]. An application comprises a fracturing fluid containing this additive. A method of fracturing a subterranean formation penetrated by a borehole comprises injecting into the borehole and into contact with the formation, at a rate and pressure sufficient to fracture the formation, a fracturing fluid containing the additive in an amount sufficient to provide fluid loss control. 

Tests showed that a fluid loss additive on a base of a sulfonated tannic-phenolic resin is effective for fluid loss control at high temperature and pressure, and it exhibits good resistance to salt and acid [868]. 

A formulation consisting of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide, and itaconic acid has been proposed [676]. Such polymers are used as fluid loss control additives for aqueous drilling fluids and are advantageous when used with lime- or gypsum-based drilling muds containing soluble calcium ions. 

The fluid loss control of aqueous, clay-based drilling mud compositions is enhanced by the addition of a hydrolyzed copolymer of acrylamide and an N-vinylamide [402], The copolymer, which is effective over a broad range of molecular weights, contains at least 5 mole-percent of the N-vinylamide units, which are hydrolyzed to N-vinylamine units. The copolymers can be made from various ratios of N-vinylamide and acrylamide by using common radical-initiated chain growth polymerization techniques. 

Horizontal completions in unconsolidated formations are being enhanced by a hydrochloric acid (HCl) breaker system for well clean up. Typically, the use of HCl in open-hole environments is avoided because of wellbore stability concerns. However, HCl successfully removes salt fluid loss control materials in wells without noticeable hole collapse [33]. 

Additives that assist the creation of a fracture include viscosifiers, such as polymers and crosslinking agents temperature stabilizers pH control agents and fluid loss control materials. Formation damage is reduced by such additives as gel breakers, biocides, surfactants, clay stabilizers, and gases. 

Naturally occurring polysaccharides and their derivatives form the predominant group of water-soluble species generally used as thickeners to impart viscosity to treating fluids [1092]. Other synthetic polymers and biopolymers have found ancillary applications. Polymers increase the viscosity of the fi ac-turing fluid in comparatively small amounts. The increase in fluid viscosity of hydraulic fracturing fluids serves for improved proppant placement and fluid loss control. Table 17 summarizes polymers suitable for fracturing fluids. 

It was discovered that viscosifying the acid showed a remarkable improvement in acid fluid loss control. The enhancement was most pronounced in very-low-permeability limestone cores. The nature of the viscosifying agent also influenced the success. Polymeric materials were more effective than surfactant-type viscosifiers [682]. 

R. Audebert, J. Janca, P. Maroy, and H. Hendriks. Chemically cross-linked polyvinyl alcohol (PVA), process for synthesizing same and its applications as a fluid loss control agent in oil fluids. Patent GB 2278359,1994. 

D. F. Bardoliwalla. Fluid loss control additives from AMPS (2-acrylamido-2-methylpropane sulfonic acid) polymers. Patent US 4622373, 1986. 

M. N. Bouts, R. A. Trompert, and A. J. Samuel. Time delayed and low-impairment fluid-loss control using a succinoglycan biopolymer with an internal acid breaker. SPE J, 2(4) 417-426, December 1997. 

L. A. Cantu and P. A. Boyd. Laboratory and field evaluation of a combined fluid-loss control additive and gel breaker for fracturing fluids. In Proceedings Volume, pages 7-16. SPE Oilfield Chem Int Symp (Houston, TX, 2/8-2/10), 1989. 

D. Crawford. High pressure high temperature (HPHT) fluid loss control aid for drilling fluids. Patent WO 0026322, 2000. 

S. C. Crema and C. H. Kucera. Cementing compositions containing a copolymer as a fluid loss control additive. Patent EP 444489, 1991. 

S. C. Crema, C. H. Kucera, G. Konrad, and H. Hartmann. Fluid loss control additives for oil well cementing compositions. Patent US 5025040, 1991. 

C. M. Garvey, A. Savoly, and A. L. Resnick. Fluid loss control additives and drilling fluids containing same. Patent US 4741843,1988. 

R. D. Gdansk . Huid properties and particle size requirements for effective acid fluid-loss control. In Proceedings Volume, pages 81-94. SPE Rocky Mountain Reg Mtg/Low Permeability Reservoirs Symp (Denver, CO, 4/26-4/28), 1993. 

M. H. Johnson. Completion fluid-loss control using particulates. In Proceedings Volume, pages 319-320. SPE Formation Damage Contr Int Symp (Lafayette, LA, 2/9-2/10), 1994. 

H. C. Lau. Laboratory development and field testing of succinoglycan as a fluid-loss-control fluid. SPE Drilling Completion, 9(4) 221-226, December 1994. 

H. Mukheijee and G. Cudney. Extension of acid fracture penetration by drastic fluid-loss control. SPE Unsolicited Paper, 1992. 

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