A system and method of decreasing contaminant concentration in an oilfield brine fluid, such as a high density completions fluid, that includes mixing the oilfield brine fluid with chlorine dioxide (ClO.sub.2). The oilfield brine fluid includes dissolved contaminant, such as iron, and one or more dissolved salts, such as selected from the group consisting of NaCl, NaBr, CaCl.sub.2, CaBr.sub.2, and ZnBr.sub.2. The mixing is for a time sufficient for the ClO.sub.2 to react with at least one component of the oilfield brine fluid to form precipitated contaminant without reacting to the one or more salts.

Iron contaminants are removed from hydrocarbon oils, and from produced water or flowback water by-products of oil and gas production, by treatment of such liquids with a composition comprising a two-tail lipid compound. The lipid binds iron to form a lipid/iron phase in the liquid, which is then removed to provide a liquid with a reduced iron level.

Embodiments of treating fluid comprising hydrocarbons, water, and polymer being produced from a hydrocarbon-bearing formation are provided. One embodiment comprises adding a concentration of a viscosity reducer to the fluid to degrade the polymer present in the fluid and adding a concentration of a neutralizer to the fluid to neutralize the viscosity reducer in the fluid. The viscosity reducer is buffered at a pH of 7 or less (e.g., at a pH of from 2 to 7, such as at a pH of from 3.5 to 7, or at a pH of from 5 to 7). The addition of the concentration of the viscosity reducer is in a sufficient quantity to allow for complete chemical degradation of the polymer prior to the addition of the concentration of the neutralizer in the fluid such that excess viscosity reducer is present in the fluid. The addition of the concentration of the neutralizer is sufficiently upstream of any surface fluid processing equipment to allow for complete neutralization of the excess viscosity reducer such that excess neutralizer is present in the fluid prior to the fluid reaching any of the surface fluid processing equipment.

Methods are provided to inhibit scale formation in oil or gas production systems. In one embodiment, the scale inhibiting treatment comprises: A) an AAA terpolymer and B) a polycarboxylate such as a polyepoxy succinic acid (PESA). The treatment can be added to these systems in the well area itself, to the well annulus and its associated tubes, casings, etc., to the oil or gas bearing subterranean formation, to injection conduits for injection of steam or fracking fluid to the subterranean formation, to the produced water, or to equipment in fluid contact with the produced water.

A method including circulating wellbore servicing fluid (WSF) downhole, passing the circulating WSF through a separator configured to separate solids therefrom, separating the plurality of particles into screened particles having a diameter greater than or equal to a mesh size and retained particles having a diameter less than the mesh size in a particulate-reduced WSF, adding a volume of second loss circulation material (LCM) composition including replenishment particles to particulate-reduced WSF to provide LCM-adjusted WSF, and introducing LCM-adjusted WSF downhole and circulating LCM-adjusted WSF. The WSF includes first LCM composition including plurality of particles having first cumulative particle size distribution (PSD). The LCM-adjusted WSF includes LCM-adjusted WSF LCMs. LCM-adjusted WSF LCMs include the retained and replenishment particles. The second LCM composition is selected to minimize a difference between a cumulative PSD of the LCM-adjusted WSF LCMs and first cumulative PSD and also minimize mass and/or volume of second LCM composition.

A process for producing a base oil composition particularly adapted for use in oil-base drilling mud compositions. The process includes contacting drilling waste containing an oil-base mud phase with a solvent to produce a mixture of liquids and solids, separating the two phases, partially evaporating the liquids phase to produce an oil base composition substantially lacking low molecular weight carbon chain compounds and also lacking significant concentrations of benzene, toluene, xylene, and/or ethyl benzene, and having increased closed-cup flashpoint when compared to the oil-base mud phase in the drilling waste. The resulting base oil has enhanced health and safety characteristics for workers interacting with and otherwise exposed to the oil base composition during transporting, conditioning or using such compositions. The base oil produced and drilling methods using the recovered and recycled mud are also described.

Taught herein is a two stage process for removing dissolved and emulsified oil from produced water (PW) from, for example, a hydrocarbon well. The first stage involves microbiological stimulation of indigenous oil degrading methanogenic microbial communities that are adapted to high salinity conditions preferably by supplying carbon dioxide and protein-rich matter (isolated soy protein) under controlled pH conditions. The second stage removes toxic metals using filters made of compressed powdered dolomite of uniform grain size. Increased levels of toxic metals removal are achieved by filtrating PW previously treated for oil. To further increase the removal efficiency of the dolomite filter, calcium and magnesium is removed from PW by the addition of lime and soda ash in a sedimentation tank, and guar gum is supplied to PW to enable the trapping of toxic metals by guar gum in small pore throats of the dolomite filter.

Embodiments of treating fluid comprising hydrocarbons, water, and polymer being produced from a hydrocarbon-bearing formation are provided. One embodiment comprises adding a concentration of a viscosity reducer to the fluid to degrade the polymer present in the fluid and adding a concentration of a neutralizer to the fluid to neutralize the viscosity reducer in the fluid. The addition of the concentration of the viscosity reducer is in a sufficient quantity to allow for complete chemical degradation of the polymer prior to the addition of the concentration of the neutralizer in the fluid such that excess viscosity reducer is present in the fluid. The addition of the concentration of the neutralizer is sufficiently upstream of any surface fluid processing equipment to allow for complete neutralization of the excess viscosity reducer such that excess neutralizer is present in the fluid prior to the fluid reaching any of the surface fluid processing equipment.

Methods and systems for treating tailings at an elevated pH using lime are disclosed herein. In some embodiments, the method comprises (i) providing a tailings stream comprising bicarbonates and a pH less than 9.0, (ii) adding a coagulant comprising calcium hydroxide to the tailings stream to form a mixture having a pH of at least 11.5 and a soluble calcium level no more than 800 mg/L, and (iii) dewatering the mixture to produce a product having a solids content of at least 40% by weight. In some embodiments, the pH and soluble calcium level of the mixture cause chemical modification of clay materials of the mixture via pozzolanic reactions. In some embodiments, the undrained shear strength of the product increases over a period of time of at least two days.

An acid spearhead formulation for mineral scale reduction that includes a sulfuric acid solution having an acidity that is substantially equivalent to a hydrochloric acid solution in an acid spearhead formulation, a sodium citrate compound, where an acid spearhead formulation for mineral scale reduction is formed, the acid spearhead formulation is disposed in a well bore to stabilize mineral scales, the acid spearhead formulation is disposed in the well bore to chelate solubilized calcium in a rock bed of the well bore, and the well bore includes a temporal thermodynamic subsurface barite cycling having a subsurface barite dissolution temporal phase, a subsurface barite transport to fractures temporal phase, a subsurface barite precipitation to fracture temporal phase and a subsurface barite dissolution to fracture space temporal phase, where the acid spearhead formulation for mineral scale reduction reacts with the well bore within the subsurface barite dissolution temporal phase.