Drilling fluids filtration

D. Tan. Test and application of drilling fluid filtrate reducer polysul-fonated humic acid resin. Oil Drilling Prod Technol, 12(l) 27-32,97-98, 1990. 

The invasion of drilling fluid filtrate into permeable zones that contain hydrocarbon adds significantly to the complexity of evaluating the... 

Filtration Properties. Drilling fluids have a natural tendency to flow into permeable formations because the borehole pressure is generally... 

Starches, used first in the late 1930s for filtration control (71), are stiU in use in the 1990s. Com starch is most commonly used in the United States. Potato starch is also used in the United States but primarily in Europe and elsewhere. Both com and potato starches are pregelatinized before dispersion in water (72). The API specifications for drilling fluid starch are listed in Table 8 (73). 

Acrylate and acrylamide polymers have several uses in drilling fluids, one of which is for filtration control. Sodium polyacrylates [9003-04-7] having molecular weights near 250,000 are exceUent temperature-stable filtration control agents for both fresh- and salt water muds, provided the concentration of water-soluble calcium is <400 mg/L (83). The calcium ions are precipitated using a carbonate such as soda ash, before adding the polyacrylate at concentrations up to ca 6 kg/m (3 Ib/bbl). 

Polyacrylates are often added to drilling fluids to increase viscosity and limit formation damage. The filter-cake is critical in preventing reservoir invasion by mud filtrate. Polymer invasion of the reservoir has been shown to have a great impact on permeability reduction [98]. The invasion of filtrate and solids in drilling in fluid can cause serious reservoir damage. 

Polydrill is a sulfonated polymer for filtration control in water-based drilling fluids [1775]. Tests demonstrated the product s thermal stability up to 200° C and its outstanding electrolyte tolerance. Polydrill can be used in NaCl-saturated drilling fluids as well as in muds containing 75,000 ppm of calcium or 100,000 ppm of magnesium. A combination of starch with Poly drill was used successfully in drilling several wells. The deepest hole was drilled with 11 to 22 kg/m of pregelatinized starch and 2.5 to 5.5 kg/m of Polydrill to a depth of 4800 m. Field experience with the calcium-tolerant starch/Polydrill system useful up to 145° C has been discussed in detail [1774]. 

Filtration control additives are added to cements for the same reason they are used in drilling fluids. Untreated cement slurries, however, have much greater filtration rates than do untreated drilling muds. Therefore it is very important to limit the loss of water from a slurry into a permeable formation. This is... 

A dispersant that can be used in drilling fluids, spacer fluids, cement slurries, completion fluids, and mixtures of drilling fluids and cement slurries controls the rheologic properties of and enhances the filtrate control in these fluids. The dispersant consists of polymers derived from monomeric residues, including low-molecular-weight olefins that may be sulfonated or phosphonated, unsaturated dicarboxylic acids, ethylenically unsaturated anhydrides, unsaturated aliphatic monocarboxylic acids, vinyl alcohols and diols, and sulfonated or phosphonated styrene. The sulfonic acid, phosphonic acid, and carboxylic acid groups on the polymers may be present in neutralized form as alkali metal or ammonium salts [192,193]. 

E. Dreveton, J. Lecourtier, D. Ballerini, and L. Choplin. Process utilizing gellan as filtrate reducer for water-based drilling fluids (procede utilisant le gellane comme reducteur de filtrat pour les fluides de forage a base d eau). Patent EP 662563,1995. 

J. Hen. Sulfonate-containing polymer/polyanionic cellulose combination for high temperature/high pressure filtration control in water base drilling fluids. Patent US 5(X)8025,1991. 

G. A. Mullen and A. Gabrysch. Synergistic mineral blends for control of filtration and rheology in silicate drilling fluids. Patent US 6248698, 2001. 

Z. Wang. Synthesis of AMPS/AM (acrylamide)A AC (vinyl acetate) copolymer—a filtration reducer of drilling fluid. Drilling Prod Technol, 22(4) 4A,55-56, July 1999. 

C. G. Zhang, M. B. Sun, W. G. Hou, and D. Sun. Study on function mechanism of filtration reducer the influence of fluid loss additive on electrical charge density of filter cake fines. Drilling Fluid Completion Fluid, 12(4) 1-5,1995. 

G. P. Zhang and H. C. Ye. AM/MA/AMPS terpolymer as non-viscosifying filtrate loss reducer for drilling fluids. Oilfield Chem, 15(3) 269-271, September 1998. 

In situ NMR measurements can be made in conjunction with down-hole fluid sampling [5, 6]. The NMR relaxation time and diffusivity can be measured under high-temperature, high-pressure reservoir conditions without loss of dissolved gases due to pressure depletion. In cases when the fluids may be contaminated by invasion of the filtrate from oil-based drilling fluids, the NMR analysis can determine when the fluid composition is approaching that of the formation [5, 6]. 

This disposal method only applies to water-based drilling fluids. The fluids may be spread directly over adjacent agricultural or forest land after adjustment of pH and ion content. Treatment may include coagulation, flocculation, filtration, and pH adjustment before spreading. A major consideration is chloride ion content. With higher chlorides, some transport of the fluid to a better disposal site may be necessary. 

Use Ceramic products, refractories, colloidal suspensions, oil-well drilling fluids, filler for rubber and plastic products, films, paper coating, decolorizing oils, temporary molds, filtration, carrier in insecticidal sprays, catalyst support. 

Filtration (Fluid Loss) Properties of Drilling Fluids... 

Static Filtration. The static fluid loss of drilling fluids is a property that is regularly measured, both at the rig site during drilling operations... 

Figure 33 shows the time dependence of the volume of static filtrate collected from a typical water-based drilling fluid. The initial volume collected at time f = 0 is termed the spurt loss and represents the uncontrolled flow of filtrate and fine solids into the filter medium the spurt loss continues until a filter cake forms on the surface of the filter medium. 

Figure 33. Time dependence of the cumulative filtrate volume from the static filtration of a bentonite-polymer drilling fluid.

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