STATEMENT OF ACKNOWLEDGEMENT

The inventors acknowledge the support provided by Department of Chemical Engineering, Center for Integrative Petroleum Research and Petroleum Engineering Department of King Fahd University of Petroleum and Minerals (KFUPM).

STATEMENT REGARDING PRIOR DISCLOSURE BY THE INVENTORS

Aspects of this technology are described in an article “Organophilic Clay-Based Drilling Fluids for Mitigation of Unconventional Shale Reservoirs Instability and Formation Damage” published in J. Energy Resour. Technol., 2019, 141(9), 093102, on Apr. 4, 2019.

BACKGROUND OF THE INVENTION

Technical Field

The present disclosure relates to a water-based drilling fluid that inhibits shale swelling. The drilling fluid contains a surfactant, a polyacrylamide, and an organophilic clay which is an ion-exchange reaction product of a smectite clay and quaternary ammonium cations.

Description of the Related Art

The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

Drilling fluids have been widely used during the exploration and extraction of oil/gas, as well as for stabilizing wellbore formations. In order to implement a time- and cost-effective drilling process, an ideal drilling fluid should demonstrate minimum fluid loss. In addition, the drilling fluid should be able to form thin impermeable filter cakes on the wall of the wellbore to stabilize reactive shale formations. High filtrate loss and thick filter cake often leads to destabilization of wellbore formations.

Drilling fluids including fracturing fluids, water-based drilling fluids, and completion fluids can interact with wellbore formations and lead to swelling of water sensitive shale formations. Many shale formations contain montmorillonite (Mt), which has a strong tendency to adsorb water molecules from the drilling fluid. The presence of interlayer cations such as Na+and Ca2+play an important role in shale swelling. Adsorption of water from the drilling fluid increases the interlayer spacing and causes shale swelling. The swelling magnitude of shale is mainly governed by factors including the ionic strength, abundance of interlayer cations, and water contents of the shale formation.

Inhibition of shale swelling has been a subject of interest in the past several decades. The knowledge of physical and chemical interactions of the drilling fluid with the formation is very important to prevent shale swelling and preserve the wellbore integrity. The swelling of wellbore causes various problems such as stuck pipe, wellbore collapse, and unsatisfactory performance of the drilling fluid [Briscoe, B. J., Luckham, P. F., and Ren, S., 1994, “The properties of drilling muds at high pressures and high temperatures,” Phil. Trans. R. Soc. Lond. A, 348(1687), pp. 179-207; Cameron, C., 2001, “Drilling fluids design and management for extended reach drilling,” SPE/IADC Middle East Drilling Technology Conference, Society of Petroleum Engineers; Omland, T., Dahl, B., Saasen, A., Taugbol, K., and Amundsen, P., 2008, “Optimized solid control provides opportunities for drilling depleted reservoirs,” J Pet Technol, 60, pp. 84-86; Ahmad, H. M., Kamal, M. S., Murtaza, M., and Al-Harthi, M. A., 2017, “Improving the Drilling Fluid Properties using Nanoparticles and Water-Soluble Polymers,” SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, Society of Petroleum Engineers; Ahmad, H. M., Kamal, M. S., and Al-Harthi, M. A., 2018, “Effect of thermal aging and electrolyte on bentonite dispersions: Rheology and morphological properties,” Journal of Molecular Liquids, 269, pp. 278-286; Ahmad, H. M., Kamal, M. S., Al-Harthi, M. A., Elkatatny, S. M., and Murtaza, M. M., 2018, “Synthesis and Experimental Investigation of Novel CNT-Polymer Nanocomposite to Enhance Borehole Stability at High Temperature Drilling Applications,” SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, Society of Petroleum Engineers; Magzoub, M., Mahmoud, M., Nasser, M., Hussein, I., Elkatatny, S., and Sultan, A., 2019, “Thermochemical Upgrading of Calcium Bentonite for Drilling Fluid Applications,” Journal of Energy Resources Technology, 141(4), p. 042902; Adewole, J. K., and Najimu, M. O., 2018, “A Study on the Effects of Date Pit-Based Additive on the Performance of Water-Based Drilling Fluid,” Journal of Energy Resources Technology, 140(5), p. 052903; and Kutlu, B., Takach, N., Ozbayoglu, E. M., Miska, S. Z., Yu, M., and Mata, C., 2017, “Drilling Fluid Density and Hydraulic Drag Reduction With Glass Bubble Additives,” Journal of Energy Resources Technology, 139(4), p. 042904].

Recent efforts have been made to study the mechanism of swelling and analyze the effect of different inhibitors on the swelling of shale formation [Sherwood, J., 1994, “A model for the flow of water and ions into swelling shale,” Langmuir: the ACS journal of surfaces and colloids, 10(7), pp. 2480-2486; Bailey, L., Keall, M., Audibert, A., and Lecourtier, J., 1994, “Effect of clay/polymer interactions on shale stabilization during drilling,” Langmuir: the ACS journal of surfaces and colloids, 10(5), pp. 1544-1549; and Yuan, W., Li, X., Pan, Z., Connell, L. D., Li, S., and He, J., 2014, “Experimental investigation of interactions between water and a lower Silurian Chinese shale,” Energy & Fuels, 28(8), pp. 4925-4933]. Despite these recent advances there is still a need to develop more efficient drilling fluid formations with superior swelling inhibition capacity.

In view of the forgoing, one objective of the present disclosure is to provide a drilling fluid formulation containing an aqueous base fluid, and additives including a gemini surfactant, a polyacrylamide, and an organophilic clay. The drilling fluid demonstrates effective shale swelling inhibition as well as improved rheology properties at elevated temperatures and pressures.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a drilling fluid, which contains (i) an aqueous base fluid, (ii) 0.01-2 wt % of a surfactant of formula (I)


or a tautomer thereof, a stereoisomer thereof, or a mixture thereof, (iii) 0.01-2 wt % of a polyacrylamide with a weight average molecular weight ranging from 320,000 g/mol to 40,000,000 g/mol, and (iv) 0.5-15 wt % of an organophilic clay including an ion-exchange reaction product of a smectite clay and a compound of formula (II)


or a salt thereof, a solvate thereof, a stereoisomer thereof, or a mixture thereof, each relative to a total weight of the drilling fluid, wherein (i) each of R1is selected from the group consisting of an optionally substituted alkyl, an optionally substituted cycloalkyl, and an optionally substituted arylalkyl, (ii) each of R2and R3, and R6and R7are independently selected from the group consisting of a hydrogen, an optionally substituted alkyl, and an optionally substituted cycloalkyl, (iii) each of R4and R5are independently selected from the group consisting of an optionally substituted alkyl, and an optionally substituted cycloalkyl, (iv) each of m is an integer in a range of 2-5, (v) n is an integer in a range of 3-8, (vi) R8, R9, R10, and R11are independently selected from the group consisting of an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted arylalkyl, and an optionally substituted aryl, and (vii) X and Y are independently an anion selected from the group consisting of a halide ion, a hexafluorophosphate ion, a trifluoromethanesulfonate ion, and a tetrafluoroborate ion.

In one embodiment, each of R1is an n-undecyl.

In one embodiment, each of R2and R3, and R6and R7are a hydrogen.

In one embodiment, each of R4and R5are a methyl.

In one embodiment, each of m is 3, and n is 4.

In one embodiment, R8, R9, R10are a methyl, and Ru is an n-octyl.

In one embodiment, the smectite clay comprises montmorillonite.

In one embodiment, at least 50 mol % of exchangeable cations of the smectite clay are ion exchanged with quaternary ammonium cations from the compound of formula (II).

In one embodiment, X and Y are a bromide.

In one embodiment, the surfactant of formula (I) is



In one embodiment, the polyacrylamide is a copolymer formed by a reaction of an acrylamide monomer, an acrylate monomer, and a hydrophobicity modifying monomer which is at least one selected from the group consisting of N-acrylamidopropyl-N,N-dimethyl-N-dodecyl ammonium chloride, N-methacrylamidopropyl-N,N-dimethyl-N-dodecyl ammonium chloride, N-acrylamidopropyl-N,N-dimethyl-N-dodecyl ammonium bromide, N-methacrylamidopropyl-N,N-dimethyl-N-dodecyl ammonium bromide, N-acrylamidopropyl-N,N-dimethyl-N-octadecyl ammonium chloride, N-methacrylamidopropyl-N,N-dimethyl-N-octadecyl ammonium chloride, N-acrylamidopropyl-N,N-dimethyl-N-octadecyl ammonium bromide, and N-methacrylamidopropyl-N,N-dimethyl-N-octadecyl ammonium bromide, with the proviso that the acrylamide monomer is structurally different from the hydrophobicity modifying monomer.

In a further embodiment, a molar ratio of the acrylamide monomer to the acrylate monomer is in a range of 3:2 to 4:1, and a molar ratio of the acrylamide monomer to the hydrophobicity modifying monomer is in a range of 200:1 to 800:1.

In one embodiment, the polyacrylamide has a weight average molecular weight ranging from 12,000,000 g/mol to 20,000,000 g/mol.

In one embodiment, the drilling fluid contains (i) the aqueous base fluid, (ii) 0.1-0.5 wt % of the surfactant of formula (I), (iii) 0.1-0.5 wt % of the polyacrylamide; and (iv) 2-8 wt % of the organophilic clay comprising the ion-exchange reaction product of a smectite clay and the compound of formula (II), each relative to a total weight of the drilling fluid.

In one embodiment, the drilling fluid has a ten-second gel strength of 6.5-13 Pa, and a ten-minute gel strength of 9-20 Pa, at a temperature of 75-250° F.

In one embodiment, the drilling fluid has a yield stress of 5-12 Pa at a temperature of 75-250° F.

In one embodiment, the drilling fluid has a storage modulus in a range of 20-50 Pa with an angular frequency of 0.1-150 rad/s at a temperature of 75-125° F. and a pressure of 250-600 psi.

According to a second aspect, the present disclosure relates to a method of drilling a subterranean geological formation. The method involves the steps of drilling the subterranean geological formation to form a wellbore therein, and circulating the drilling fluid of the first aspect into the wellbore during the drilling.

In one embodiment, the wellbore has a temperature in a range of 75-400° F., and a pressure in a range of 250-1,000 psi.

In one embodiment, the subterranean geological formation is a shale formation.

The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

