阅读说明：本技术 用于油基钻井液的层状双氢氧化物 (Layered double hydroxide for oil-based drilling fluids ) 是由 木萨拉特·哈利玛·穆罕默德 休·克里斯托弗·格林威尔 安德鲁·怀廷 马诺哈拉·古蒂约尔·维拉巴 于 2018-08-09 设计创作，主要内容包括：制备油基钻井液的方法和油基钻井液的组合物。油基钻井液包含基础油连续相、水性分散相以及至少一种流变改性剂,其中基础油连续相包含基础油,流变改性剂包括改性的镁/铝碳酸盐层状双氢氧化物(Mg/Al-CO<Sub>3</Sub>191 LDH)化合物。(Methods of making oil-based drilling fluids and compositions of oil-based drilling fluids. The oil-based drilling fluid comprises a base oil continuous phase, an aqueous dispersed phase and at least one rheology modifier, wherein the base oil continuous phase comprises a base oil, and the rheology modifier comprises a modified magnesium/aluminum carbonate layered double hydroxide (Mg/Al-CO) 3 191L DH).)

1. An oil-based drilling fluid comprising:

a base oil continuous phase, wherein the base oil continuous phase comprises a base oil;

an aqueous dispersed phase; and

at least one rheology modifier comprising a modified magnesium/aluminum carbonate layered double hydroxide (Mg/Al-CO)₃L DH) compounds.

2. The oil-base drilling fluid of claim 1 wherein the magnesium/aluminum carbonate layered double hydroxide (Mg/Al-CO)₃L DH) the compound was prepared by:

mixing a magnesium compound, an aluminum compound, and an aqueous solution to form an initial solution;

adding at least one basic compound to the initial solution to form a reaction solution, the at least one basic compound comprising a carbonate or bicarbonate;

optionally adjusting the pH with a solution comprising; and

heating the reaction solution at a reaction temperature for a reaction time to form the Mg/Al-CO₃L DH compound.

3. The oil-base drilling fluid of any one of claims 1 or 2 wherein the base oil is selected from base oils selected from: a synthetic, diesel or mineral oil comprising an ester or olefin, wherein the synthetic, diesel or mineral oil comprises a hydrocarbon selected from the group consisting of: normal paraffins, iso-paraffins, cyclic paraffins, branched paraffins or mixtures thereof.

4. The oil-base drilling fluid of any one of claims 1 to 3 further comprising at least one additive selected from the group consisting of: emulsifiers, wetting agents, alkalinity controlling agents, fluid loss controlling agents, suspending agents, weight regulators, density regulators, or combinations thereof.

5. The oil-base drilling fluid of any one of claims 1 to 4 comprising 0.1 to 1.0 wt.% of a rheology modifier based on the total weight of the oil-base drilling fluid.

6. An oil-base drilling fluid as claimed in any one of claims 1 to 5 wherein said aqueous dispersed phase comprises brine selected from: calcium chloride, calcium bromide, sodium chloride, sodium bromide, and combinations thereof.

7. The oil-base drilling fluid of any one of claims 1 to 6 wherein the oil-base drilling fluid exhibits physical properties suitable for use of the oil-base drilling fluid under high pressure, high temperature conditions during drilling operations.

8. The oil-base drilling fluid of claim 7 wherein the high pressure, high temperature conditions during drilling operations include a wellbore pressure greater than 10,000psi and a wellbore temperature greater than 300 ° F.

9. A method of making an oil-based drilling fluid, the method comprising:

mixing a base oil, at least one emulsifier and at least one wetting agent to form a base oil continuous phase; and

adding at least one rheology modifier to the base oil continuous phase to form an oil-based drilling fluid, wherein the at least one rheology modifier comprises a modified magnesium/aluminum carbonate layered double hydroxide compound.

10. The method of claim 9 wherein the oil-based drilling fluid further comprises at least one additive selected from the group consisting of: a fluid loss control additive, a brine solution, at least one weighting additive, a rheology modifier, and combinations thereof.

11. The method of claim 9, wherein the modified magnesium/aluminum carbonate (Mg/Al-CO)₃) The compound was prepared by:

mixing a magnesium compound, an aluminum compound, and an aqueous solution to form an initial solution;

adding at least one basic compound to the initial solution to form a reaction solution, the at least one basic compound comprising a carbonate or bicarbonate;

optionally adjusting the pH with a solution comprising; and

heating the reaction solution at a reaction temperature for a reaction time to form the Mg/Al-CO₃L DH compound.

12. The method of any of claims 9 to 11, wherein the base oil continuous phase comprises a base oil selected from the group consisting of: a synthetic, diesel or mineral oil comprising an ester or olefin, wherein the synthetic, diesel or mineral oil comprises a hydrocarbon selected from the group consisting of: normal paraffins, iso-paraffins, cyclic paraffins, branched paraffins or mixtures thereof.

13. The method of any one of claims 9 to 12, wherein the brine solution is selected from the group consisting of calcium chloride, calcium bromide, sodium chloride, sodium bromide, and combinations thereof.

14. A method of drilling in a subterranean formation under high pressure, high temperature conditions, the method comprising:

providing or using an oil-based drilling fluid according to any one of claims 1 to 8 when drilling a wellbore in the subterranean formation.

15. The method of claim 14, wherein the high pressure high temperature conditions comprise a wellbore pressure greater than 10,000psi and a wellbore temperature greater than 300 ° F.

16. A method of drilling a subterranean well, the method comprising:

operating drilling in a wellbore in the presence of an oil-based drilling fluid comprising:

a base oil;

at least one additive selected from an emulsifier, a weighting material, a fluid loss additive, a viscosifier, or a basic compound; and

0.1 to 1 wt.% of a magnesium/aluminum carbonate layered double hydroxide compound based on the total weight of the drilling fluid.

17. The method of claim 16, further comprising adding the magnesium/aluminum carbonate layered double hydroxide compound to the drilling fluid prior to or during operational drilling in the wellbore.

Technical Field

Embodiments of the present disclosure generally relate to oil-based drilling fluids for use in high pressure and high temperature drilling operations. More specifically, embodiments of the present disclosure relate to oil-based drilling fluids comprising surface-modified magnesium/aluminum carbonate layered double hydroxide compounds as rheology modifiers.

Background

Drilling operations to drill new wellbores for hydrocarbon production, for example, include the conventional practice of continuously circulating a drilling fluid (alternatively referred to as drilling mud) through the wellbore during the drilling operation. The drilling fluid is pumped into the drill pipe to the bottom of the borehole, then flows up through the annulus between the borehole wall and the drill pipe and finally out of the borehole where it is recovered for secondary treatment. Specifically, the drilling fluid is mechanically or chemically treated to remove the captured solids and cuttings from the drilling fluid, and then the drilling fluid is recirculated back through the wellbore.

Given the circulation characteristics of the drilling fluid and its function of capturing solids and cuttings during drilling operations, the drilling fluid must flow freely at a relatively low viscosity to facilitate pumping while having sufficient material to retain and transport cuttings and other solids. If circulation of the drilling fluid ceases, the drilling fluid must also have sufficient gel strength to suspend solids and cuttings in order to prevent solids from accumulating at the bottom of the wellbore. Solids accumulated at the bottom of the wellbore can cause sticking and physical blockage of the drilling fluid flow path.

Deep well drilling is complicated by geological conditions involving high pressures and temperatures (HPHT). Industry-defined definitions of HPHT conditions typically include wellbore temperatures above 300 degrees fahrenheit (deg.f) (149 degrees celsius (deg.c)) and wellbore pressures above 10,000 pounds-force square inches (psi) (68.9 megapascals (MPa)).

Disclosure of Invention

Accordingly, there is a continuing need for drilling fluids and rheology modifiers for drilling fluids that are thermally stable under HPHT conditions and have rheological properties suitable for well treatment. Rheology modifiers, when added to oil-based drilling fluids, can enhance rheological properties such as "brittle gel" properties and shear thinning behavior.

Accordingly, some embodiments of the present disclosure include an oil-based drilling fluid comprising a base oil continuous phase comprising a base oil, an aqueous dispersed phase, and at least one rheology modifier comprising a modified magnesium/aluminum carbonate layered double hydroxide (Mg/Al-CO)₃L DH) compounds.

Other embodiments of the present disclosure include a method for preparing an oil-based drilling fluid, wherein the method comprises mixing a base oil, at least one emulsifier, and at least one wetting agent to form a base oil continuous phase; and adding at least one rheology modifier to the base oil continuous phase to form the oil-based drilling fluid, wherein the at least one rheology modifier comprises a modified magnesium/aluminum carbonate layered double hydroxide compound.

Detailed Description

Specific embodiments of drilling fluids having rheology modifiers will now be described. It should be understood that the rheology modifiers and drilling fluids of the present disclosure may be embodied in different forms and should not be construed as limited to the specific embodiments set forth in the present disclosure. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

To drill a subterranean well, a drill string including a drill bit and drill collars that apply weight to the drill bit may be inserted into a pre-drilled hole and rotated to cause the drill bit to cut into the rock at the bottom of the hole. Drilling operations produce rock fragments. To remove rock debris from the bottom of the wellbore, a drilling fluid (such as an oil-based drilling fluid) is pumped down the drill string to the drill bit. The drilling fluid cools the drill bit, provides lubrication, and lifts rock fragments, known as drill cuttings, off the drill bit. The drilling fluid carries the cuttings up as it is recirculated back to the surface. At the surface, the drill cuttings are removed from the drilling fluid by a secondary operation and the drilling fluid is recirculated back down the drill string to the bottom of the wellbore to collect additional drill cuttings.

Drilling fluids include drilling mud, packer fluids, and completion fluids. In general, drilling fluids have many functions, with different types of drilling fluids being dedicated to a particular function or functions. In one or more embodiments, the oil-based drilling fluid suspends drill cuttings and weight material, and the drill cuttings are conveyed to the wellbore surface with the oil-based drilling fluid. In addition, oil-based drilling fluids may absorb gases in the wellbore, such as carbon dioxide (CO)₂) Hydrogen sulfide (H)₂S) and methane (CH)₄) And conveys them to the wellbore surface for release, sequestration, or burn-off. The oil-based drilling fluid may additionally provide buoyancy to the drill string, relieving tension on the drill string as the length of the wellbore increases. In one or more embodiments, the oil-based drilling fluid also provides cooling and lubrication functions for cooling and lubricating the drill bit and drill string used in the drilling operation. In other embodiments, the oil-based drilling fluid may control the subterranean pressure. In particular, the oil-based drilling fluid may provide hydrostatic pressure in the wellbore to provide support to the sidewall of the wellbore and prevent the sidewall from collapsing or collapsing on the drill string. Additionally, the oil-based drilling fluid may provide hydrostatic pressure in the wellbore to prevent drillingFluids in a downhole formation flow into a wellbore during operation.

Under certain extreme downhole conditions, such as excessive temperatures or difficult formations, some properties of the drilling fluid may be altered. For example, interaction of the drilling fluid with formations having swelling clays, excess solids content, or both, or subjecting the drilling fluid to extreme downhole temperatures may cause the drilling fluid to thicken or thin, excessively increase or decrease in viscosity, or any combination of these. For example, drilling fluids used in High Pressure and High Temperature (HPHT) operations may be subjected to wellbore temperatures above 300 ° F (149 ℃) and wellbore pressures above 10,000psi (68.9MPa), which is an industry-defined definition of HPHT conditions. Under HPHT conditions, the drilling fluid may decompose or undergo undesirable changes in rheology.

Embodiments of the oil-based drilling fluid are formulated to provide a fluid having a rheology suitable for HPHT drilling operations. In particular, the oil-based drilling fluids are formulated to have a higher viscosity at lower shear rates than commercially available HPHT oil-based drilling fluids, and a lower viscosity at high shear rates than commercially available HPHT oil-based drilling fluids. Low shear rates are generally below 10s^-1And the high shear rate is usually more than 100s^-1. The higher viscosity at low shear rates increases the ability of oil-based drilling fluids to retain drill cuttings when drilling operations are stopped. Conversely, the lower viscosity of the oil-based drilling fluid at high shear rates reduces the energy required to circulate the oil-based drilling fluid during drilling operations.

In one or more embodiments, the oil-based drilling fluid includes a base oil phase, an aqueous dispersed phase, and at least one rheology modifier that includes a carbonate layered double hydroxide (L DH) compound, in some embodiments, the carbonate L DH compound is or includes a magnesium/aluminum carbonate layered double hydroxide (Mg/Al-CO)₃L DH) compound Mg/Al-CO₃L the DH compound may have an empirical formula [ Mg_1-xAl_x(OH)₂](CO₃)_x/3·mH₂O, wherein x is 0.1 to 0.4 and m is 0.1 to 0.6. In some embodiments, Mg/Al-CO₃L DH compound per se, or Mg/Al-CO₃L DH compounds, for example, may be modified in some embodiments of the oil-based drilling fluid, the oil-based drilling fluid may include from 0.05 wt.% to 5.0 wt.%, from 0.1 wt.% to 1.0 wt.%, or from 0.1 wt.% to 0.5 wt.% of the magnesium/aluminum carbonate L DH compound, based on the total weight of the oil-based drilling fluid.

Mg/Al-CO₃L particles of DH rheology modifier can be prepared by forming a slurry or aqueous solution of a magnesium compound and an aluminum compound one or more basic compounds can be added to the slurry or aqueous solution to form a reaction mixture at least one basic compound can include a carbonate or bicarbonate₃L DH. aluminum compounds may include, for example, Al (OH)₃、Al₂O₃、Al(NO₃)₃Or AlCl₃. The magnesium compound may include, for example, Mg (OH)₂、Mg(NO₃)₂、MgCl₂Or MgO. In one example, the magnesium compound may be Mg (NO)₃)₂And the aluminum salt may be Al (NO)₃)₃. In some embodiments, the magnesium or aluminum salt may be a hydrate, such as, for example, Al (NO)₃)₃·9H₂O or Mg (NO)₃)₃·6H₂And O. The basic compound includes a carbonate or bicarbonate. Examples of carbonates include Na₂CO₃And NaHCO₃. In addition to the carbonate or bicarbonate, the basic compound may optionally include a base, such as Mg (OH)₂、Al(OH)₃Or NaOH.

Mg/Al-CO for drilling fluids of the present disclosure₃L preparation of the DH compound rheology modifier can include additional or optional steps optionally, pH. slurry, aqueous solution or reaction mixture of the slurry, aqueous solution or reaction mixture can have an initial pH of 7 to 12, and the initial pH can be adjusted to 7 to 10.5, 7 to 10, 9 to 12, 9 to 10.5, 9 to 10, 9.5 to 12, 9.5 to 10.5, 9.5 to 10, 7.5 to 9, 7.5 to 9.5 or 10 to 12 with one or more basic compounds or acidic solutions such as NaOH adjusting the pH reduces corrosion of the pipe.

For preparing Mg/Al-CO₃L the initial slurry, aqueous solution, or reaction mixture of the DH compound may have a Mg/Al molar ratio of 5:1, 4:1, 3:1, or 2:1 the carbonate ion is added in a molar ratio relative to the Mg/Al ratio in one or more embodiments, the molar ratio of the carbonate ion may be equal to the molar ratio of Al in the compound.

For preparing Mg/Al-CO₃L the DH compound may be reacted at a temperature of from 40 ℃ to 180 ℃ or from 140 ℃ to 160 ℃ and for a time of at least 12 hours in some embodiments, the reaction time is from 12 hours to 50 hours or from 16 hours to 25 hours.

The base oil continuous phase may be any fluid, such as an oil or a solution containing an oil and one or more organic or inorganic compounds dissolved in or otherwise fully miscible with the oil. The base oil continuous phase may comprise at least one base oil. The base oil continuous phase may also comprise esters, ethers, acetals, dialkyl carbonates, hydrocarbons, or any combination of these.

The base oil may be selected from natural petroleum products or synthetic oils. Synthetic oils or natural petroleum products may be composed of hydrocarbons such as normal paraffins, isoparaffins, cyclic paraffins, branched paraffins, or mixtures thereof. Base oils may include oils derived from petroleum, such as mineral oil; diesel oil; linear or branched olefins; a polyolefin; a fatty acid ester; linear, branched or cyclic alkyl ethers of fatty acids; other petroleum derived oils, or any combination of these. The base oil may also include oils derived from animals or plants, such as, for example, saffron oil (safra oil). The base oil may also include other oils such as, but not limited to, polydiorganosiloxanes, siloxanes, organosiloxanes, other silicone-based oils, or combinations of these oils. In some embodiments, the base oil may be any oil included in conventional drilling fluids for drilling applications.

In some embodiments, the oil-based drilling fluid may comprise at least 10.0 wt.% base oil or may comprise from 10.0 wt.% to 20.0 wt.% base oil, based on the total weight of the oil-based drilling fluid. In other embodiments, the oil-based drilling fluid may comprise about 13.0 wt.% to 17.0 wt.% or 14.0 wt.% to 16 wt.% base oil, based on the total weight of the oil-based drilling fluid.

The aqueous dispersed phase of the oil-based drilling fluid may be any fluid that is not completely miscible in the base oil continuous phase. For example, the aqueous dispersed phase may be water or a solution containing water and one or more organic or inorganic compounds dissolved in or otherwise completely miscible with water. In some embodiments, the aqueous dispersed phase may contain water, including fresh water, well water, filtered water, distilled water, seawater, brine, produced water, formation brine, other types of water, or combinations of these. In embodiments, the aqueous dispersed phase may contain saline, including natural and synthetic saline. For example, the brine includes water and a salt selected from the group consisting of calcium chloride, calcium bromide, sodium chloride, sodium bromide, and combinations thereof. In some embodiments, the aqueous dispersed phase may include water soluble organic compounds as additives or impurities dissolved in water. The water-soluble organic compound may include: alcohols, organic acids, amines, aldehydes, ketones, esters or other polar water-soluble organic compounds.

In one or more embodiments, the oil-based drilling fluid may comprise from about 1.0 wt.% to about 10.0 wt.% of the aqueous discontinuous phase, based on the total weight of the oil-based drilling fluid. In other embodiments, the oil-based drilling fluid may include from 2.0 wt.% to 7.0 wt.% or from 2.0 wt.% to 5 wt.% of the aqueous discontinuous phase.

The oil-based drilling fluid may optionally include one or more additives. Exemplary additives include one or more wetting agents, one or more emulsifiers, one or more other rheology modifiers, one or more fluid loss control additives, or one or more weighting additives. The oil-based drilling fluid may optionally include pH adjusters, electrolytes, glycols, glycerols, dispersion aids, corrosion inhibitors, defoamers, or other additives or combinations of additives known or used in conventional drilling fluids.

In one or more embodiments, the oil-based drilling fluid may include a surfactant, such as a wetting agent, to enhance the stability of the suspension or emulsion in the oil-based drilling fluid. Suitable wetting agents may include fatty acids, organic phosphates, modifiedLinear imidazolines, amidoamines, alkyl aromatic sulfates and sulfonates. For exampleCommercially available from M-I SWACO (houston, texas) is an oil-based wetting agent and co-emulsifier that can be used to wet fines and drilling solids to prevent water wetting of the solids. In addition to this, the present invention is,thermal stability, rheological stability, filtration control, emulsion stability of the wellbore fluid may be improved.An exemplary oil-based drilling fluid may optionally include 0.1 to 2.0 wt.% of a wetting agent, based on the total weight of the oil-based drilling fluid, in some embodiments, the oil-based drilling fluid may optionally include 0.25 to 0.75 wt.% of a wetting agent, based on the total weight of the oil-based drilling fluidThe oil-based drilling fluid may optionally include other wetting agents known or used in conventional drilling fluids.

In some embodiments, one or more emulsifiers may be added to the oil-based drilling fluid examples of emulsifiers include surfactants, detergents, lignosulfonates, lignin compounds, and materials derived from Tall Oil Fatty Acids (TOFA)^TMAnd MU L XT commercially available from M-I SWACO.

In one or more embodiments, the oil-based drilling fluid may optionally include one or more emulsifiers, and the total amount of emulsifiers in the oil-based drilling fluid may be 0.00 wt.% to 5 wt.%, 0.1 wt.% to 2.5 wt.%, 0.1 wt.% to 2.0 wt.%, 0.1 wt.% to 1 wt.%, 0.5 wt.% to 2.5 wt.%, 0.5 wt.% to 2 wt.%, 0.5 wt.% to 1.5 wt.%, 0.5 wt.% to 1 wt.%, 0.75 wt.% to 2.5 wt.%, or 0.75 wt.% to 2 wt.%, based on the total weight of the drilling fluid.

The oil-based drilling fluid may optionally include a fluid loss control agent that reduces the amount of filtrate lost from the drilling fluid into the subterranean formation^TM、VERSALIG^TM、ECOTROL^TMRD、ONETROL^TMHT, EMI 789 and NOVATECH^TMF, all commercially available from MI SWACO (houston, texas, usa); andcommercially available from Halliburton Energy Services, Inc. in some embodiments, the oil-based drilling fluid may optionally include ONETRO L^TMHT and ECOTRO L^TMRD, both. In some embodiments, when a fluid loss control agent is included in the oil-based drilling fluid, the total amount of fluid loss control agent may be from about 0.5 wt.% to about 3.0 wt.% of the oil-based drilling fluid, based on the total weight of the drilling fluid. In other embodiments, the oil-based drilling fluid may comprise 0.9 wt.% to 2.5 wt.% or 1.0 wt.% to 2.0 wt.%.

The oil-based drilling fluid may optionally include a suspending agent that adjusts the viscosity of the oil-based drilling fluid to create a yield point sufficient to suspend all drilling fluid components at low shear rates and thus avoid settling of the drilling fluid components. Examples of suspending agents include fatty acids and fibrous materials. In embodiments where the oil-based drilling fluid includes a suspending agent, the oil-based drilling fluid may comprise from about 0.0 wt.% to about 1.0 wt.% or from 0.01 to 0.5 wt.%, based on the total weight of the drilling fluid.

In some embodiments, the oil-based drilling fluid may optionally include a weighting materialAnd (5) feeding. The weight material may be a particulate solid selected to have a Specific Gravity (SG) sufficient to increase the density of the drilling fluid by a desired amount. The weighting material may be used to control formation pressure and help resist the effects of collapsing or expanding shale which may be encountered in the stress zone. Any substance that is denser than water and does not adversely affect other properties of the drilling fluid may be used as the weight material. The weight material may have a Specific Gravity (SG) of 2 to 6. Examples of weighting materials include, but are not limited to, barite (BaSO)₄) (ii) a Hematite (Fe)₂O₃) (ii) a Calcium carbonate (CaCO)₃) (ii) a Siderite; iron oxides produced, such as ilmenite (FeO. TiO)₂) Siderite (FeCO)₃) Celestite (SrSO)₄) And dolomite (CaCO)₃·MgCO₃) (ii) a Galena (PbS), magnetite (Fe)₃O₄) And other weight materials, or any combination of these weight materials. Some embodiments of the oil-based drilling fluid may include barite as a weighting material.

The optional weighting material or density modifier of the oil-based drilling fluid may increase the weight of the oil-based drilling fluid, the density of the oil-based drilling fluid, or both. In some embodiments, the oil-based drilling fluid may include 1 to 75 wt.%, 20 to 80 wt.%, 20 to 75 wt.%, 50 to 80 wt.%, 50 to 75 wt.%, 60 to 80 wt.%, 60 to 75 wt.%, 65 to 80 wt.%, or 70 to 80 wt.% weight gain material, based on the total weight of the oil-based drilling fluid. Typically, the amount of optional weighting material in the oil-based drilling fluid is large enough to achieve the desired oil-based drilling fluid density, and small enough to avoid the oil-based drilling fluid failing to circulate through the wellbore.

The oil-based drilling fluid may optionally include a pH adjuster. In embodiments, the oil-based drilling fluid may optionally include a basic compound that increases the pH of the oil-based drilling fluid. Examples of alkaline compounds include, but are not limited to, lime (calcium hydroxide or calcium oxide), soda ash (sodium carbonate), sodium hydroxide, potassium hydroxide, other strong bases, or combinations of these alkaline compounds. During drilling operations, the basic compound may react with gases in the oil-based drilling fluid, such as, for example, CO₂Or H₂S, to prevent gasA component of a body-hydrolyzed oil-based drilling fluid. Some example oil-based drilling fluids may optionally include 0.1 wt.% to 1.5 wt.%, 0.4 wt.% to 1 wt.%, or 0.6 wt.% to 0.8 wt.% lime. In embodiments, the oil-based drilling fluid may have a pH of 7 to 12, 7 to 10.5, 7 to 10, 9 to 12, 9 to 10.5, 9 to 10, 9.5 to 12, 9.5 to 10.5, 9.5 to 10, 7.5 to 9, 7.5 to 9.5, or 10 to 12. In some embodiments, the oil-based drilling fluid may have a pH of 9 to 10.5.

In some embodiments, in addition to Mg/Al-CO₃L DH compounds, the oil-based drilling fluid may optionally include one or more rheology modifiers such as viscosifiers or clays examples of viscosifiers may include, but are not limited to, bentonite, organophilic clays, polyacrylamide, polyanionic cellulose, or combinations of these viscosifiers42. Except for Mg/Al-CO₃L DH compounds, the exemplary oil-based drilling fluid may optionally include 0.0 to 2 wt.% based on the total weight of the oil-based drilling fluid of a rheology modifier in some embodiments, the oil-based drilling fluid may optionally include 0.25 to 0.5 wt.% based on the total weight of the oil-based drilling fluid of each of VERSAGE L HT and Bentone 42.

Having described the oil-based drilling fluid in accordance with various embodiments, an illustrative method for preparing an oil-based drilling fluid will now be described. In one or more embodiments, the method for preparing an oil-based drilling fluid comprises mixing a base oil, optionally at least one emulsifier, and optionally at least one wetting agent to form a base oil continuous phase. Adding at least one rheology modifier to a base oil continuous phase to form an oil-based drilling fluid. As previously mentioned, the at least one rheology modifier comprises Mg/Al-CO₃L DH compound.

Optionally, the method for preparing an oil-based drilling fluid may comprise adding at least one additive; additives include fluid loss control additives, brine solutions, weighting materials, and combinations of these additives. The fluid loss control additive may be added in an amount such that the final oil-based drilling fluid provided comprises from about 0.5 wt.% to about 3.0 wt.%, or from 0.9 wt.% to 2.0 wt.%, or from 1.0 wt.% to 1.5 wt.% of the fluid loss control additive, based on the total weight of the oil-based drilling fluid. After the additives are added, the oil-based drilling fluid is mixed by a suitable stirring method, such as by mechanical stirring.

The brine solution may be added in an amount such that the final oil-based drilling fluid provided comprises from about 1.0 wt.% to about 10.0 wt.%, or from about 2.0 wt.% to about 6.0 wt.% brine, based on the total weight of the oil-based drilling fluid.

The weight material may be added to the fourth mixture in an amount such that the final oil-based drilling fluid provided contains 1 wt.% to 75 wt.%, 20 wt.% to 80 wt.%, 20 wt.% to 75 wt.%, 50 wt.% to 80 wt.%, 50 wt.% to 75 wt.%, 60 wt.% to 80 wt.%, 60 wt.% to 75 wt.%, 65 wt.% to 80 wt.%, 65 wt.% to 78 wt.%, or 70 wt.% to 80 wt.% weight material based on the total weight of the oil-based drilling fluid.

The previously described oil-based drilling fluids, including those prepared according to embodiments of the methods for preparing oil-based drilling fluids in the present disclosure, as well as those prepared according to embodiments of the present disclosure but by other industry-acceptable techniques understood by those of ordinary skill, may be well-suited for use in drilling operations for subterranean formations, particularly drilling operations conducted under HPHT conditions with wellbore pressures greater than 10,000psi and wellbore temperatures greater than 300 ° F (149 ℃). Accordingly, embodiments of a method for drilling a well in a subterranean formation under high pressure, high temperature conditions may include drilling a wellbore in the subterranean formation using an oil-based drilling fluid.

In a method of drilling a well in a subterranean formation,the oil-based drilling fluid comprises modified Mg/Al-CO₃As used herein, "comparative drilling fluid" refers to a drilling fluid having all of the same components as an oil-based drilling fluid and the same weight ratios of each other as the same components in the oil-based drilling fluid to each other, but with the difference that (1) the comparative drilling fluid lacks Mg/Al-CO₃L DH compound, and (2) adjusting one or both of the amount of base oil or the amount of weighting agent in the comparison drilling fluid to match the specific gravity of the comparison drilling fluid to the specific gravity of the oil-based drilling fluid and to match the oil-to-water ratio of the oil-based drilling fluid.