EP4623040A1

EP4623040A1 - Liquid weighting agents for oil-based fluids

Info

Publication number: EP4623040A1
Application number: EP23828580.3A
Authority: EP
Inventors: Yunqi Liu; Joseph Baker; Huaxiang Yang; Garrett NIELSEN; Donovan THOMPSON; Gilles L. NUMKAM; Tse-Chong Wu
Original assignee: Albemarle Corp
Current assignee: Albemarle Corp
Priority date: 2022-11-22
Filing date: 2023-11-15
Publication date: 2025-10-01
Also published as: WO2024112545A1; IL321011A

Abstract

This invention provides compositions that can be used as liquid weighting agents.

Description

LIQUID WEIGHTING AGENTS FOR OIL-BASED FLUIDS

TECHNICAL FIELD

[0001] This invention relates to liquid weighting agents for oilfield applications.

BACKGROUND

[0002] In some oilfield operations, the well fluids need to have a relatively high density, so one or more ingredients are added to the well fluid to increase the density of the well fluid. Brines are typically used to increase the density of aqueous well fluids, but some well fluids are oil-based. In oil-based fluids, solid weighting agents are often used to increase the well fluid density, but solid weighting agents often block pores and decrease production from the formation.

[0003] Liquid weighting agents are an alternative to solid weighting agents for oil-based well fluids, but may not be miscible with the oil-based fluid, may form emulsions with the oil-based well fluid, and/or cause solids formation. There is a need for liquid weighting agents that do not form emulsions and/or cause precipitation.

SUMMARY OF THE INVENTION

[0004] This invention provides liquid weighting agents that increase the density of oilbased well fluids, and can provide high density fluids. To achieve the increased density, the liquid weighting agent is made part of the oil-based well fluid. The liquid weighting agents of the invention can increase the densities of an oil-based well fluid to about 14.5 pounds per gallon (1.74 kg/L) or more. In addition to increasing the density of the fluid in which they are present, liquid weighting agents permit use of increased drill speeds. Another advantage of these liquid weighting agents is a greater amount of oil produced from the formation. Still another advantage of the liquid weighting agents of the present invention is that they do not significantly alter the fluid loss properties of formulations in which they are present. Yet another advantage provided by some of the liquid weighting agents of the invention is a minimal effect on the viscosity of the fluids to which they are introduced or combined; in some instances, liquid weighting agents of the invention reduce the viscosity of the fluids to which they are introduced or combined, so a change of equipment to larger pumps is not required. Another advantage provided by the liquid weighting agents of the invention is that they can be a component of optically clear fluids. [0005] An embodiment of this invention is a liquid weighting agent containing two or more bromine atoms and having a bromine content of about 35 wt% or more. The liquid weighting agent is selected from a) a bromine-containing saturated cyclic diether comprising two or more bromine atoms, and a saturated ring comprising two oxygen atoms and four or more carbon atoms, the saturated ring having one or more hydrocarbyl substituents, each bound to a carbon atom of the saturated ring, wherein each bromine atom is bound to a hydrocarbyl substituent in a position on the hydrocarbyl substituent that does not have beta hydrogen atoms; b) a bromine-containing aromatic diether comprising one phenyl ring having two or three bromine atoms bound to the phenyl ring and at least one oxygen-containing group bound to the phenyl ring via an oxygen atom, with the proviso that when there is only one oxygen-containing group, the oxygen-containing group is an alkoxyether group; and c) any two or more of the foregoing.

[0006] Another embodiment of this invention is an oil-based well fluid comprising a liquid weighting agent selected from the bromine-containing ethers described above.

[0007] These and other embodiments and features of this invention will be still further apparent from the ensuing description and appended claims.

FURTHER DETAILED DESCRIPTION OF THE INVENTION

[0008] As used throughout this document, the phrase "aromatic carbon atom" refers to a carbon atom that is part of an aromatic ring.

[0009] Throughout this document, both "ppg" and "Ib/gal" are abbreviations for pounds per gallon.

[0010] Some of the liquid weighting agents of this invention are usable as oil-miscible weighting agents (OMWA). As used throughout this document, the term "miscible" means that emulsions and/or separate phases are not observed in a 50:50 weight mixture of one or more of the liquid weighting agents of this invention (total of 50 wt%) and an oil (50 wt%) after the mixture has been kept at 0°C for one week. Similarly, as used throughout this document, the term "partially miscible" means that emulsions and/or separate phases are not observed in a 50:50 weight mixture of one or more of the liquid weighting agents of this invention (total of 50 wt%) and an oil (50 wt%) after the mixture has been kept at room temperature for one week.

[0011] The liquid weighting agents of the present invention are generally miscible with oil-based well fluids. In the practice of this invention, the liquid weighting agents are often in a mixture with an oil. Oils with which the liquid weighting agents are optionally mixed are oils which usually have a viscosity of about 7 cP or less, and a density typically about 0.7 g/mL to about 0.9 g/mL. The amount of liquid weighting agent in the oil can be about 0.1 wt% to 100 wt%; when more than one liquid weighting agent is used, the amount refers to the total amount of liquid weighting agents. When there is 100 wt% liquid weighting agent of the invention, no other substance is present with the liquid weighting agent. Preferred amounts of liquid weighting agent in the oil depend on the desired density, and there is typically about 0. 1 wt% to 100 wt% liquid weighting agent in a mixture with an oil, more often about 0.1 to about 99.9 wt%, preferably about 2 wt% to about 99.9 wt% liquid weighting agent in a mixture with an oil. The mixture of oil and the liquid weighting agent(s) usually have a viscosity of about 10 cP or less, and a density typically about 0.7 g/mL to about 1.8 g/mL.

[0012] The liquid weighting agents of this invention share some overall characteristics. In these liquid weighting agents, there are two or more bromine atoms in the molecule, and a bromine content of about 35 wt% or more. The bromine content in the liquid weighting agent is preferably about 35 wt% to about 70 wt%, more preferably about 40 wt% to about 65 wt%, relative to the total weight of the liquid weighting agent.

[0013] In some embodiments, the liquid weighting agent is a bromine-containing saturated cyclic diether comprising two or more bromine atoms, and a saturated ring comprising two oxygen atoms and three or more carbon atoms, the saturated ring having one or more hydrocarbyl substituents, each bound to a carbon atom of the saturated ring, wherein each bromine atom is bound to a hydrocarbyl substituent. The bromine- containing saturated cyclic diether has four or more carbon atoms, preferably four to about fifteen carbon atoms, more preferably four to about twelve carbon atoms, still more preferably five to about ten carbon atoms, in the molecule.

[0014] The saturated ring of the cyclic diether can be a five-membered, six-membered, seven-membered ring, or a larger ring; five-membered and six-membered rings are preferred, and the saturated ring is often a 1,2-dioxololane, 1,3-dioxololane, 1,4- dioxololane, 1,2-dioxane, 1,3-dioxane, or 1,4-dioxane ring; preferred is a 1.3 dioxane ring. [0015] There are one or more hydrocarbyl substituents on the saturated ring; when there is more than one hydrocarbyl substituent, they can be on the same or different carbon atoms of the saturated ring. Preferably, the saturated ring has one to about three hydrocarbyl substituents. The hydrocarbyl substituents on the saturated ring can be saturated or unsaturated, straight chain, branched, or aromatic; preferably the hydrocarbyl portions are saturated straight chains. Suitable hydrocarbyl portions include methyl, ethyl, ethenyl, n- propyl, 2-propyl, n-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, and phenyl; methyl and phenyl are preferred.

[0016] The bromine atoms are located on the hydrocarbyl substituent(s) of the saturated ring. When there is more than one hydrocarbyl substituent on the saturated ring, the bromine atoms can be on the same or different hydrocarbyl substituent; preferably, the bromine atoms are on different hydrocarbyl substituents. The bromine atoms are in positions on the hydrocarbyl substituent which do not have beta hydrogen atoms.

[0017] Preferably, there are two to about four, more preferably, two to about three, bromine atoms in the bromine-containing saturated cyclic diethers. Bromine-containing saturated cyclic diethers of the invention typically have a bromine content of about 40 wt% or more, preferably about 45 wt% or more, and often have densities of about 1.50 g/mL or more.

[0018] Suitable cyclic diethers in the practice of this invention include 4,4-bis(2- bromoethyl)- 1 ,2-dioxolane, 4,5 -bis(3 -bromo-n-propyl)- 1 ,3 -dioxolane, 5,5- bis(bromomethyl)-l,2-dioxane, 5,5-bis(bromomethyl)-2-ethyl-l,3-dioxane, and 2-methyl- 5-(l,2-dibromoethyl)-l,4-dioxane. Preferred cyclic diethers include 5,5-bis(bromomethyl)- 1,2-dioxane and 5,5-bis(bromomethyl)-2-ethyl-l,3-dioxane, especially 5,5- bis(bromomethyl)-2-ethyl- 1 ,3-dioxane.

[0019] In some embodiments, the liquid weighting agent is a bromine-containing aromatic diether comprising one phenyl ring having two or three bromine atoms bound to the phenyl ring and at least one oxygen-containing group bound to the phenyl ring via an oxygen atom, with the proviso that when there is only one oxygen-containing group, the oxygencontaining group is an alkoxyether group. There are preferably eight to about twenty carbon atoms, more preferably eight to about sixteen carbon atoms, in the bromine-containing aromatic diester molecule. When there are two bromine atoms on the phenyl ring, the bromine atoms are preferably ortho or para relative to each other. The bromine-containing aromatic diethers typically have a bromine content of about 35 wt% or more, preferably about 40 wt% or more, more preferably about 45 wt% or more.

[0020] When there is only one oxygen-containing group in the bromine-containing aromatic diether, In the alkoxyether groups, the hydrocarbyl portions of the groups are saturated. The alkoxyether groups have two to about eight carbon atoms, preferably three to about six carbon atoms, more preferably two to about three oxygen atoms. More preferably, the alkoxyether group containing two or more oxygen atoms has an ethylene unit between each pair of oxygen atoms, and the terminal group is preferably methyl or ethyl. Preferred alkoxyether groups include 2-methoxyethoxy and 2-ethoxyethoxy. When there is only one oxygen-containing group in the brominated benzene molecule, at least one bromine atom is preferably adjacent ortho) to the group containing two or more oxygen atoms; in some preferred embodiments, two bromine atoms are adjacent to the alkoxyether group.

[0021] When there is more than one oxygen-containing group on the phenyl ring of the bromine-containing aromatic diether, one of the oxygen-containing groups is a hydrocarbyloxy group. More preferably, the hydrocarbyloxy group is an alkoxy group having one to about four carbon atoms, preferably one or two carbon atoms. Preferred hydrocarbyloxy groups include methoxy and ethoxy.

[0022] When there are two oxygen-containing groups on the phenyl ring of the brominated benzenes, preferably one of the oxygen-containing groups is an alkoxyether group and the other oxygen- containing group is a hydrocarbyloxy group; preferences for alkoxyether groups and hydrocarbyloxy groups are as described above. More preferably, there are two bromine atoms on the phenyl ring when there are two oxygen-containing groups on the phenyl ring of the bromine-containing aromatic diether.

[0023] Suitable bromine-containing aromatic diethers in the practice of this invention include l,3-dibromo-4-(2-ethoxy)ethoxybenzene, l,2-dibromo-4-butoxy-5-ethoxybenzene 2,4- dibromo-5 -methoxy- 1 -[(2-ethoxy)ethoxy]benzene, 2, 4-dibromo-5 -ethoxy- 1-[(2- ethoxy)ethoxy]benzene, 2,4-dibromo- 1 -[(2-ethoxy)ethoxy]benzene, 2,6-dibromo- 1 - [(2- ethoxy)ethoxy]benzene; preferred bromine-containing aromatic diethers include 1,3- dibromo-4-(2-ethoxy)ethoxybenzene, and 1 ,2-dibromo-4-butoxy-5-ethoxybenzene.

[0024] Combinations of any two or more of the above liquid weighting agents can be used in the practice of this invention. [0025] Some of the liquid weighting agents of the invention have enough high- temperature thermal stability that they can be used in HPHT (high pressure, high temperature) conditions. HPHT conditions are usually defined as a temperature greater than about 250°F (121 °C) and a pore pressure greater than about 0.8 psi/ft (15.3 Ib/gal). In addition, the liquid weighting agents of the invention, when used in offshore applications, need low-temperature thermal stability because temperatures at the sea floor can be around 5°C.

[0026] It is often useful to include one or more optional additives with the liquid weighting agents, especially in a well fluid, and the inclusion of such additives is within the scope of this invention. Optional additives can include, for example, other weighting agents, corrosion inhibitors, lubricants, pH control additives, surfactants, and/or solvents.

[0027] Preferred types of optional additives in the practice of this invention are unsaturated diesters and saturated triesters that do not contain bromine. When the additive is an unsaturated diester, the unsaturated diester has at least eight carbon atoms and is represented by the formula where R^a and R^c are hydrocarbyl groups, and R^b is an alkene-containing moiety. R^a and R^c can be straight chain, branched, cyclic, or aromatic; preferably the hydrocarbyl group is a straight chain. Suitable hydrocarbyl groups include methyl, ethyl, n-propyl, 2-propyl, n- butyl, pentyl, cyclopentyl, hexyl, and cyclohexyl; ethyl and n-propyl are preferred. R^b preferably has four to about eight carbon atoms, more preferably four to about six carbon atoms; suitable alkene-containing moieties include 2-butene, 2-pentene, 2-hexene, 3- hexene, 2-octene 3-octene, and 4-octene; preferred alkene-containing moieties include 2- butuene.

[0028] When the additive is a saturated triester, the saturated triester has at least seven carbon atoms and is represented by the formula where R^d, R^c, R^f, and R^g are hydrocarbyl groups. R^d, R^f, and R^g can be straight chain, branched, or cyclic; preferably the hydrocarbyl group is a straight chain. Suitable hydrocarbyl groups include methyl, ethyl, n-propyl, 2-propyl, n-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, and phenyl; ethyl and n-propyl are preferred. R^c can be branched or cyclic, or aromatic; preferably R^c is a saturated branched chain. Suitable hydrocarbyl groups include propyl, butyl, 2-pentyl, 3-pentyl, cyclopentyl, 2-hexyl, 3, -hexyl, and cyclohexyl; 2- propyl is a preferred group.

[0029] Suitable unsaturated diesters that do not contain bromine include but-2-ene-l,4- diyl diacetate, but-2-ene- 1 ,4-diyl bis(propanoate), but-2-ene- 1 ,4-diyl bis(butyrate), but-2- ene-l,4-diyl bis(pentanoate), pent-2-ene- 1,5 -diyl diacetate, pent-3 -ene- 1,5 -diyl diacetate, pent-3-ene- 1 ,5-diyl bis(propanoate); preferred is but-2-ene- 1 ,4-diyl bis(butyrate). Suitable saturated triesters that do not contain bromine include propane- 1,2, 3 -triyl triacetate, propane- 1, 2, 3-triyl propanoate, propane- 1,2, 3 -triyl tributyrate; preferred is propane- 1,2,3 - triyl tributyrate. Combinations of any two or more unsaturated diesters and/or saturated triesters can be used in the practice of the invention.

[0030] Processes for forming mixtures of a liquid weighting agent and an oil, which oil can be a paraffin, mineral, olefinic, or ester oil, comprise combining the oil and the liquid weighting agent in any order. For example, an oil and the liquid weighting agent(s) can be added sequentially, or they can be introduced to a vessel or location simultaneously.

[0031] Any optional additives that are included can be combined with the liquid weighting agents in any convenient manner. When the liquid weighting agent is in a mixture with an oil, optional additives can be added before, during, and/or after formation of the mixture of an oil and the liquid weighting agent.

[0032] In some embodiments of the invention, a mixture of an oil and one or more liquid weighting agents of the invention is solids-free.

[0033] Although mixtures comprising liquid weighting agents are preferably solids-free, in some instances, one or more liquid weighting agents of the invention can be part of a mixture containing one or more solids, for example a solid weighting agent such as barite, if desired. In these instances, the use of a liquid weighting agent of the invention will reduce the amount of solid weighting agent needed to achieve the desired density.

[0034] In some well fluids, the presence of some solids is not disadvantageous. Calcium carbonate is often present as a suspension in a well fluid. The calcium carbonate often forms a filter cake that prevents the drilling fluid from entering the formation. After drilling, an acid treatment can be used to remove the calcium carbonate filter cake.

[0035] One or more liquid weighting agents of the invention can be combined with an oilbased well fluid. The oil-based well fluid can be a drilling fluid; completion fluids fluids including but not limited to a packer fluid, a screen running fluid, or a carrier fluid; a (reservoir) drill-in fluid; a tractor fluid; a camera fluid; or workover fluids fluids including but not limited to a coiled tubing drilling fluid. The liquid weighting agents of the invention can be combined with the well fluid alone or in admixture with one or more other additives and/or in a mixture with an oil.

[0036] The liquid weighting agents of the invention can be used as secondary fluids ("kill fluids") to minimize or relieve sustained casing pressure in a wellbore annulus. The term "annular fluid" refers to the first fluid, which is present in the wellbore annulus before the second fluid is introduced. The second fluid can be introduced at the wellhead or below the surface of the annular fluid; subsurface introduction of the kill fluid is generally preferred. For treating sustained casing pressure, immiscibility refers to the non-mixing or substantial non-mixing of the liquid weighting agents and the (aqueous) annular fluid. See in this connection International Publication WO 2015/100004.

[0037] The liquid weighting agents of this invention can be used as additives for hydraulic fluids. Preferably, the liquid weighting agent of the invention is about 35 wt% or more relative to the total weight of the hydraulic fluid and the liquid weighting agent of the invention. In terms of bromine content, there is about 20 wt% to about 70 wt% bromine relative to the total weight of the hydraulic fluid and the liquid weighting agent of the invention. Other additives, such as antioxidants, lubricity agents, and metal deactivators, may also be present in the hydraulic fluid.

[0038] The molecule 5,5-bis(bromomethyl)-2-ethyl-l,3-dioxane is a new composition of matter.

[0039] The following examples are presented for purposes of illustration, and are not intended to impose limitations on the scope of this invention. EXAMPLE 1

Synthesis of 5,5-bis(bromomethyl)-2-ethyl-l,3-dioxane

[0040] Into a 2-L 4-neck round-bottom flask were charged bis-bromomethyl-1,3- propanediol (655 g), p-toluenesulfonic acid monohydrate (5.0 g), and toluene (1.2 L). While stirring the ingredients in the round-bottom flask, propionaldehyde (186 g) was added via addition funnel during 15 to 20 minutes under nitrogen. The reaction mixture was then heated to 84°C and kept at 84 to 92°C for 2 hours while collecting water in a Dean-Stark apparatus. After stirring the reaction mixture at 84 to 92°C for another 2 hours under nitrogen, the reaction mixture was cooled to room temperature. The reaction mixture was washed with saturated sodium bicarbonate (4x300 mL) and then with water (400 mL). The phases were allowed to separate, and the separated organic layer was dried over MgSCL. After filtration to remove the solids, the toluene was removed from the organic layer on rotavap under vacuum (~ 60 torr), and 723 grams of the product were obtained as a colorless liquid with a density of 1.64 g/mL. A 50:50 wt/wt mixture of this product with an oil had not phase separated after one week at -18°C.

TESTING PROCEDURES

[0041] Admixture preparation. To a 600 mL beaker were added a synthetic oil fluid (Saraline® 185V), and a liquid weighting agent of the invention. An overhead lab mixer (Silverson, model L5M-A) is lowered into the liquid and slowly turned up to 4000 rpm. Various ingredients were then added sequentially, stirring for a period of time after each addition. The mixture was transferred to a stand mixer (Hamilton Beach), usually before the addition of calcium carbonate. When a liquid polymeric viscosifier was added, ice cubes were held against the outside of the Hamilton Beach stand mixer during the mixing of the liquid polymeric viscosifier to control the temperature because the standard procedure requires testing at room temperature (20 to 25 °C), and the mixing procedure usually increased the temperature to over 110°F (43.3°C). Sample components, amounts thereof, mixer type, and mixing time after each addition are summarized in the Tables below.

[0042] Admixture testing. The American Petroleum Institute Recommended Practice 13B-2 (API RP 13B-2) testing procedures for field testing oil-based drilling fluids were followed to obtain properties of the mixture formed as described above. The sample was then hot-rolled overnight to simulate heat aging of the sample in actual use. The properties of the sample were then tested again using the same testing procedures. [0043] Fluid loss testing. The API Fluid Loss Experiment was conducted at approximately 250°F (121°C). The sample was heated to ~250°F (121°C) over 1.5 hours, and was passed through a 10-micron filter disk (Fann®) in a filter press (Model 387, Fann Instrument Company) at ~250°F for 30 minutes with a 500 psi (3.45 MPa) pressure differential. The API fluid loss volume for fluid loss is double the total volume measured due to the surface area of the filter disk. Results of the Fluid Loss Experiment are summarized in Table 3 below. The filter cake thickness was measured.

[0044] The HPHT fluid loss procedure was as follows:

1. A synthetic disk or rock core was placed into the testing cell.

2. The fluid to be tested was poured into the testing cell (typically 350 to 500 mL of fluid).

3. The testing cell was placed in a heating jacket and heated to the testing temperature (300°F for most fluids).

4. A pressure, dependent on the testing temperature, was applied to the testing cell during heating of the testing cell.

5. Once the temperature has been reached, a pressure difference of 500 psi (3.45 MPa) was applied across the testing cell, and then valves were opened at both ends; the pressure difference pushed the fluid being tested through the synthetic disk or rock core.

6. The amount of fluid flowing through the disk was measured and recorded at various points in time.

7. The test continued for 30 minutes.

8. At the conclusion of the experiments the valves were closed, and the heating jacket was turned off. The testing cell was allowed to cool before removing the remaining fluid. Then the synthetic disk or rock core was removed and examined to observe the filter cake (solids left by the fluid as it traveled into or through the disk or rock core).

[0045] The components and testing results for a 5,5-bis(bromomethyl)-2-ethyl-l,3- dioxane mixture are summarized in Tables 1A-C below. The hot -rolling temperature was 105°C. The fluid loss filter cake had a 3/32-inch (0.238 cm) thickness, and the fluid loss test was conducted at 250°F (121°C). TABLE 1A

TABLE IB

TABLE 1C

[0046] Another set of components and testing results for a 5,5-bis(bromomethyl)-2-ethyl- 1,3 -dioxane mixture are summarized in Tables 2A-B below. The hot-rolling temperature was 105°C. The fluid loss filter cake had a 3/32-inch (0.238 cm) thickness.

TABLE 2A

TABLE 2B

[0047] Several sets of components and testing results for a 5,5-bis(bromomethyl)-2-ethyl- 1 ,3-dioxane mixture are summarized in Tables 3Ai-3Dii below. The hot-rolling temperature was 105°C.

TABLE 3Ai

TABLE 3Aii TABLE 3Bi

TABLE 3Bii

TABLE 3Ci

TABLE 3Cii

TABLE 3Ciii

TABLE 3Di

TABLE 3Dii

[0048] Further embodiments of the invention include, without limitation:

[0049] A) A liquid weighting agent containing two or more bromine atoms and having a bromine content of about 35 wt% or more, which liquid weighting agent is selected from a) a bromine-containing saturated cyclic diether comprising two or more bromine atoms, and a saturated ring comprising two oxygen atoms and four or more carbon atoms, the saturated ring having one or more hydrocarbyl substituents, each bound to a carbon atom of the saturated ring, wherein each bromine atom is bound to a hydrocarbyl substituent in a position on the hydrocarbyl substituent that does not have beta hydrogen atoms; b) a bromine-containing aromatic diether comprising one phenyl ring having two or three bromine atoms bound to the phenyl ring and at least one oxygen-containing group bound to the phenyl ring via an oxygen atom, with the proviso that when there is only one oxygen-containing group, the oxygen-containing group is an alkoxyether group; and c) any two or more of the foregoing.

[0050] B) A liquid weighting agent as in A) wherein the bromine- containing saturated cyclic diether has four to about fifteen carbon atoms in the molecule and/or has a saturated ring which is a five-membered ring or a six-membered ring, and/or has one to about three hydrocarbyl substituents on the saturated ring.

[0051] C) A liquid weighting agent as in A) wherein the bromine-containing aromatic diether has about eight to about twenty carbon atoms in the molecule and/or has one oxygencontaining group bound to the phenyl ring, which oxygen-containing group is an alkoxyether group, and optionally at least one bromine atom is adjacent to the oxygencontaining group.

[0052] D) A liquid weighting agent as in A) wherein the bromine-containing aromatic diether has about eight to about twenty carbon atoms in the molecule and/or has two oxygencontaining groups bound to the phenyl ring, which oxygen-containing groups are an alkoxyether group and a hydrocarbyloxy group.

[0053] E) A liquid weighting agent as in any of A)-D) wherein bromine content is about 40 wt% or more.

[0054] F) A liquid weighting agent as in any of A)-E) which is 5,5-bis(bromomethyl)-2- ethy 1-1, 3 -dioxane, l,3-dibromo-4-(2-ethoxy)ethoxybenzene, and/or l,2-dibromo-4-butoxy- 5 -ethoxybenzene.

[0055] G) A liquid weighting agent as in any of A)-F) wherein one or more additives selected from unsaturated diesters that do not contain bromine and/or saturated triesters that do not contain bromine are included with the liquid weighting agent, wherein the unsaturated diester has at least eight carbon atoms and is represented by the formula where R^a and R^c are hydrocarbyl groups, and R^b is an alkene-containing moiety, and wherein the saturated triester has at least seven carbon atoms and is represented by the formula where R^d, R^c, R^f, and R^g are hydrocarbyl groups.

[0056] H) A liquid weighting agent as in G) wherein the unsaturated diester is but-2-ene- 1 ,4-diyl bis(butyrate), and wherein the saturated triester is propane- 1, 2, 3-triyl tributyrate.

[0057] I) A liquid weighting agent as in any of A)-H) which is in a mixture with an oil, wherein there is about 0. 1 to about 99.9 wt% liquid weighting agent in the mixture with the oil; or in combination with a hydraulic fluid.

[0058] J) An oil-based well fluid comprising a liquid weighting agent of any of A)-H), optionally wherein the well fluid is a drilling fluid, a completion fluid, a drill-in fluid, a tractor fluid, a camera fluid, or a workover fluid.

[0059] K) A method of treating a wellbore, said method comprising introducing into the wellbore a fluid comprising a liquid weighting agent as in any of A)-H), optionally wherein the fluid is a drilling fluid, a completion fluid, a drill-in fluid, a tractor fluid, a camera fluid, or a workover fluid.

[0060] L) A method for minimizing or relieving a sustained casing pressure in an annulus of a wellbore, wherein the annulus contains a first fluid having a density, the method comprising introducing a second fluid into the annulus, wherein the second fluid has a density greater than the density of the first fluid and the second fluid is immiscible with the first fluid, characterized in that the second fluid comprises a liquid weighting agent of any ofA)-H).

[0061] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e.g., another component, a solvent, or etc. . It matters not what chemical changes, transformations and/or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and/or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and/or ingredients in the present tense ("comprises", "is", etc. , the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and/or ingredients in accordance with the present disclosure. The fact that a substance, component or ingredient may have lost its original identity through a chemical reaction or transformation during the course of contacting, blending or mixing operations, if conducted in accordance with this disclosure and with ordinary skill of a chemist, is thus of no practical concern.

[0062] The invention may comprise, consist, or consist essentially of the materials and/or procedures recited herein.

[0063] As used herein, the term "about" modifying the quantity of an ingredient in the compositions of the invention or employed in the methods of the invention refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like. The term about also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term "about", the claims include equivalents to the quantities.

[0064] Except as may be expressly otherwise indicated, the article "a" or "an" if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article "a" or "an" if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise.

[0065] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.

Claims

THAT WHICH IS CLAIMED IS:

1. A liquid weighting agent containing two or more bromine atoms and having a bromine content of about 35 wt% or more, which liquid weighting agent is selected from a) a bromine-containing saturated cyclic diether comprising two or more bromine atoms, and a saturated ring comprising two oxygen atoms and four or more carbon atoms, the saturated ring having one or more hydrocarbyl substituents, each bound to a carbon atom of the saturated ring, wherein each bromine atom is bound to a hydrocarbyl substituent in a position on the hydrocarbyl substituent that does not have beta hydrogen atoms; b) a bromine-containing aromatic diether comprising one phenyl ring having two or three bromine atoms bound to the phenyl ring and at least one oxygen-containing group bound to the phenyl ring via an oxygen atom, with the proviso that when there is only one oxygen-containing group, the oxygen-containing group is an alkoxyether group; and c) any two or more of the foregoing.

2. A liquid weighting agent as in Claim 1 wherein the bromine-containing saturated cyclic diether has four to about fifteen carbon atoms in the molecule; the bromine-containing aromatic diether has about eight to about twenty carbon atoms in the molecule.

3. A liquid weighting agent as in Claim 1 wherein the bromine-containing saturated cyclic diether has a saturated ring which is a fivemembered ring or a six-membered ring; the bromine-containing aromatic diether has one oxygen-containing group bound to the phenyl ring, which oxygen-containing group is an alkoxyether group.

4. A liquid weighting agent as in Claim 1 wherein the bromine-containing saturated cyclic diether has one to about three hydrocarbyl substituents on the saturated ring; the bromine-containing aromatic diether has one oxygen-containing group bound to the phenyl ring, and at least one bromine atom is adjacent to the oxygen-containing group.

5. A liquid weighting agent as in Claim 1 wherein the bromine-containing aromatic diether has two oxygen-containing groups bound to the phenyl ring, which oxygencontaining groups are an alkoxyether group and a hydrocarbyloxy group.

6. A liquid weighting agent as in any of Claims 1-5 wherein bromine content is about 40 wt% or more.

7. A liquid weighting agent as in any of Claims 1-6 which is 5,5-bis(bromomethyl)-2- ethy 1-1, 3 -dioxane, l,3-dibromo-4-(2-ethoxy)ethoxybenzene, and/or l,2-dibromo-4-butoxy- 5 -ethoxybenzene.

8. A liquid weighting agent as in any of Claims 1-7 wherein one or more additives selected from unsaturated diesters that do not contain bromine and/or saturated triesters that do not contain bromine are included with the liquid weighting agent, wherein the unsaturated diester has at least eight carbon atoms and is represented by the formula where R^a and R^c are hydrocarbyl groups, and R^b is an alkene-containing moiety, and wherein the saturated triester has at least seven carbon atoms and is represented by the formula where R^d, R^c, R^f, and R^g are hydrocarbyl groups.

9. A liquid weighting agent as in Claim 8 wherein the unsaturated diester is but-2-ene- 1 ,4-diyl bis(butyrate), and wherein the saturated triester is propane- 1, 2, 3-triyl tributyrate.

10. A liquid weighting agent as in any of Claims 1-9 in a mixture with an oil, wherein there is about 0. 1 to about 99.9 wt% liquid weighting agent in the mixture with the oil.

11. A liquid weighting agent as in any of Claims 1-9 in combination with a hydraulic fluid.

12. An oil-based well fluid comprising a liquid weighting agent of any of Claims 1-9.

13. An oil-based well fluid as in Claim 12 wherein the well fluid is a drilling fluid, a completion fluid, a drill-in fluid, a tractor fluid, a camera fluid, or a workover fluid.

14. A method of treating a wellbore, said method comprising introducing into the wellbore a fluid comprising a liquid weighting agent as in any of Claims 1-9.

15. A method as in Claim 14 wherein the fluid is a drilling fluid, a completion fluid, a drill-in fluid, a tractor fluid, a camera fluid, or a workover fluid.

16. A method for minimizing or relieving a sustained casing pressure in an annulus of a wellbore, wherein the annulus contains a first fluid having a density, the method comprising introducing a second fluid into the annulus, wherein the second fluid has a density greater than the density of the first fluid and the second fluid is immiscible with the first fluid, characterized in that the second fluid comprises a liquid weighting agent of any of Claims 1-9.

17. The following molecule as a new composition of matter: 5,5-bis(bromomethyl)-2- ethyl- 1 ,3 -dioxane.