Rheology drilling fluids

R. C. Portnoy. Anionic copolymers for improved control of drilling fluid rheology. Patent GB 2174402, 1986. 

Stabilizing agents are used to maintain drilling fluid rheological properties at highly elevated downhole temperatures. Chromium and chromium-free lignosulfonates, polyglycol ethers, sodium polystyrene sulfonate-co-maleic anhydride), and a melanin polymer have been used in this application. Additives such as sodium diethyldi-thiocarbamate have been used to stabilize aqueous polysaccharides such as xanthan gum (18). 

Demirdal, B., Miska, S., Takach, N.E. Cunha, J.C. 2007. Drilling Fluids Rheological and Volumetric Characterization Under Downhole Conditions. Paper SPE 108111 presented at the SPE Latin American and Caribbean Petroleum Engineering Conference, Buenos Aires, Argentina, 15-18 April. 

Drilling grade - Barite for well drilling fluids is typically a 200 mesh product with specific gravity of at least 4.2 (i.e., >90% BaS04 ). Color is not critical, but water-soluble alkaline earth metals are controlled so as not to interfere with drilling fluid rheology. 

Water-Based Muds. About 85% of all drilling fluids are water-based systems. The types depend on the composition of the water phase (pH, ionic content, etc), viscosity builders (clays or polymers), and rheological control agents (deflocculants or dispersants (qv)). 

Acrylamide polymers are used as multipurpose additives in the oil-producing industry. Introduction of polymers into drilling fluids-drilling muds improves the rheological properties of the fluids in question, positively affects the size of suspended particles, and adds to filterability of well preparation to operation. Another important function is soil structure formation, which imparts additional strength to the well walls. A positive effect is also observed in secondary oil production, where acrylamide polymers additives improve the mobility of aqueous brines injections, which contribute to... 

Rheological Classification of Drilling Fluids 829. Flow Regimes 830. Principle of Additive Pressures 834. Friction Pressure Loss Calculations 836. Pressure Loss Through Bit Nozzles 839. 

Sources of Toxicity. There are three contributing mechanisms of toxicity in drilling fluids, chemistry of mud mixing and treatment, storage/disposal practices, and drilled rock. The first group conventionally has been known the best because it includes products deliberately added to the system to build and maintain the rheology and stability of drilling fluids. 

DRILLING MUD HYDRAULICS Rheological Classification of Drilling Fluids... 

Zinc compounds have a high reactivity with regard to H2S and therefore are suitable for the quantitative removal of even small amounts of hydrogen sulfide [1831]. However, at high temperatures they may negatively affect the rheology of drilling fluids. 

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]. 

A mixture of sulfonated styrene-maleic anhydride copolymer and polymers prepared from acrylic acid or acrylamide and their derivatives [759] are dispersants for drilling fluids. The rheologic characteristics of aqueous well drilling fluids are enhanced by incorporating into the fluids small amounts of sulfonated styrene-itaconic acid copolymers [761] and an acrylic acid or acrylamide polymer [755]. 

D. Dino and J. Thompson. Organophilic clay additives and oil well drilling fluids with less temperature dependent rheological properties containing said additives. Patent EP 1138740A, 2001. 

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

D. G. Peiffer, J. Bock, and J. Elward-Berry. Thermally stable hydro-phobically associating rheological control additives for water-based drilling fluids. Patent US 5096603,1992. 

Xanthan, used in EOR trials in the USA, and still being considered elsewhere, has found a niche in drilling fluids, which, together with other oilfield uses, accounts for some 2000 tons per year. Xanthan solutions have several useful properties they display a highly pseudoplastic rheology, are tolerant to salt, and have good thermal stability. There was we felt, however, some scope for improvement. 

Of even more economic importance is the rheological impact of the addition of KC1 to conventional water-base drilling fluids. KC1 causes undesirable increases in both yield point and gel strength that can only be eliminated by chemical disperants or by dilution with fresh water. Dilution in turn requires more KC1 for clay inhibition, and the cycle continues with mud costs escalating exponentially. 

Tests were conducted to compare the effect of KC1 and TKPP on the rheology of an unweighted (nondispersed) and a weighted (dispersed) drilling fluid. All fluids were mixed in an industry standard Hamilton Beach mixer. The rheology of each fluid was then measured in a Fann viscometer at 120°F at 300 rpm and 600 rpm. 

The results of these tests and the fluid formulations axe shown in Table IV. The adverse effect on fluid rheology of adding potassium, KC1, Test B, and TKPP, Test C, is evident. Both salts cause increases in yield point, YP, and initial gel strength. TKPP produced only about half as much increase as did KC1 and can be added in much higher concentrations before the rheological properties of the drilling mud become unacceptable. 

The results of the latest research into helical flow of viscoplastic fluids (media characterized by ultimate stress or yield point ) have been systematized and reported most comprehensively in a recent preprint by Z. P. Schulman, V. N. Zad-vornyh, A. I. Litvinov 15). The authors have obtained a closed system of equations independent of a specific type of rheological model of the viscoplastic medium. The equations are represented in a criterion form and permit the calculation of the required characteristics of the helical flow of a specific fluid. For example, calculations have been performed with respect to generalized Schulman s model16) which represents adequately the behavior of various paint compoditions, drilling fluids, pulps, food masses, cement and clay suspensions and a number of other non-Newtonian media characterized by both pseudoplastic and dilatant properties. 

Ayeni, K. Osisanya, S.O. Evaluation of Commonly Used Fluid Rheological Models Using Developed Drilling Hydraulic Simulator in Proc. 5th Canadian International Petroleum Conference, The Petroleum Society Calgary,... 

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