The present invention relates to the well drilling field in petrochemical industry, and discloses a high-density water-based drilling fluid suitable for horizontal shale gas wells comprising a nano-plugging agent, a bionic wall bracing agent, a bionic shale inhibitor, a filler, an emulsifier, and an amphiphobic wettability reversal agent, wherein, the nano-plugging agent is modified silicon dioxide nano-particle, and its modifying group includes a modifying copolymer chain; the bionic wall bracing agent is carboxymethyl chitosan with a dopamine-derived group grafted on its main chain; the bionic shale inhibitor is composed of structural units of arginine and structural units of lysine; the filler consists of calcium carbonate of 1,600-2,500 mesh, calcium carbonate of 1,050-1,500 mesh, and calcium carbonate of 500-1,000 mesh at a weight ratio of 1:0.55-6:0.55-6; and the amphiphobic wettability reversal agent is a dual-cation fluorocarbon surfactant. The drilling fluid provided herein is suitable for use in shale gas mining.

The present invention relates to the well drilling field in petrochemical industry, and discloses an environment-friendly water-based drilling fluid applicable to horizontal shale gas wells comprising a nano-plugging agent, a bionic wall bracing agent, a bionic shale inhibitor, a filler, an emulsifier, and an amphiphobic wettability reversal agent, wherein, the nano-plugging agent is modified silicon dioxide nano-particle, and its modifying group includes an acrylic copolymer chain; the bionic wall bracing agent is carboxymethyl chitosan with a dopamine-derived group grafted on its main chain; the bionic shale inhibitor is composed of structural units of arginine and structural units of lysine; the filler consists of calcium carbonate of 1,600-2,500 mesh, calcium carbonate of 1,050-1,500 mesh, and calcium carbonate of 500-1,000 mesh at a weight ratio of 1:0.55-6:0.55-6; and the amphiphobic wettability reversal agent is a dual-cation fluorocarbon surfactant. The drilling fluid provided in the present invention has high temperature-resistance, high plugging and high inhibition performance, is environment friendly, especially has high density, and is applicable to shale gas mining.

An ultralow-permeability agent contains a structural unit provided by styryl hydrophobic monomer, maleic anhydride and acrylamide; the drilling fluid contains two or more of water, sodium bentonite, Pac-Lv, the ultralow-permeability agent, calcium carbonate, one-way plugging agent, white asphalt and barite which are stored in a mixed manner or independently stored. When the amphiphilic block polymer provided by the invention is used as the ultralow-permeability agent of the intelligent temporary plugging type water-based drilling fluid, the self-adaptive characteristic is realized; according to the amphiphilic block polymer, temporary plugging layer gaps formed in pore and throats by plugging materials in drilling fluid can be fully filled under the condition that the sizes and the distribution of the pore and throats of reservoirs are not required to be clear, so that the permeability of temporary plugging layer is greatly reduced, ultralow-permeability is realized.

A method includes adding a clay to water to form a suspension of clay in water, the clay including pieces of clay having an average diameter of at least 2 μm; adding a dispersant to the suspension of clay in water to form a drilling fluid; and injecting the drilling fluid into a well. In the drilling fluid, the dispersant interacts with the clay to form nanoscale particles of clay having an average diameter of less than 500 nm.

A method includes adding a clay to water to form a suspension of clay in water, the clay including pieces of clay having an average diameter of at least 2 μm; adding a dispersant to the suspension of clay in water to form a drilling fluid; and injecting the drilling fluid into a well. In the drilling fluid, the dispersant interacts with the clay to form nanoscale particles of clay having an average diameter of less than 500 nm.

Shale inhibiting additives for subterranean drilling and/or treatment fluids that include polyvinyl alcohol (PVA) are provided. In some embodiments, the methods include: providing a treatment fluid including an aqueous base fluid and a shale inhibiting additive including polyvinyl alcohol; introducing the treatment fluid into at least a portion of a subterranean formation to contact at least a portion of the subterranean formation that comprises shale; and allowing the shale inhibiting additive to interact with the shale in the subterranean formation to at least partially inhibit the shale.

The invention relates to the field of drilling fluid, in particular to a saturated salt water drilling fluid of salt response type intelligent polymer and preparation method thereof. The drilling fluid contains two or more of the following components stored in admixture or separately: bentonite, NaOH, KCl, calcium carbonate, barite, NaCl, supramolecular fluid loss additive, supramolecular shear-enhancing agent, plugging agent, coating agent and water. The drilling fluid provided by the invention has the characteristics of salt response and self-assembly, can keep rheological properties such as rapid recovery of the sheared structure, low extreme high shear rate viscosity, good shear dilution property and the like in a high-salt environment, has good fluid loss reduction performance, reservoir protection performance and debris dispersion inhibition performance, and has good temperature resistance and pollution resistance performance.

The invention relates to the field of drilling fluid, in particular to a saturated salt water drilling fluid of salt response type intelligent polymer and preparation method thereof. The drilling fluid contains two or more of the following components stored in admixture or separately: bentonite, NaOH, KCl, calcium carbonate, barite, NaCl, supramolecular fluid loss additive, supramolecular shear-enhancing agent, plugging agent, coating agent and water. The drilling fluid provided by the invention has the characteristics of salt response and self-assembly, can keep rheological properties such as rapid recovery of the sheared structure, low extreme high shear rate viscosity, good shear dilution property and the like in a high-salt environment, has good fluid loss reduction performance, reservoir protection performance and debris dispersion inhibition performance, and has good temperature resistance and pollution resistance performance.

The present invention relates to the technical field of petroleum drilling. An intermediate product of a reservoir protecting agent, a reservoir protecting agent, a preparing method and use thereof, a drilling fluid and use thereof are disclosed. The intermediate product of a reservoir protecting agent is made of raw materials comprising acrylamide, a cationic monomer, a cross-linking agent, an initiator, a toughening material and water, and based on the raw materials of 100 parts by weight, the use amounts of the acrylamide, the cationic monomer, the cross-linking agent, the initiator and the toughening material are respectively 8-30, 1-10, 0.01-0.5, 0.01-0.1, 5-25 parts by weight. The reservoir protecting agent includes the intermediate product of the present invention, base, salt, and water, and based on the reservoir protecting agent of 100 parts by weight, the use amounts of the intermediate product, base, and salt are respectively 5-40, 1-10, and 1-12 parts by weight. The reservoir protecting agent of the present invention has a good blocking effect and can improve the capability of the drilling fluid to protect the reservoir, enhance the capability of the drilling fluid to stabilize well walls.

Drilling fluid compositions include invert emulsion fluids having an oleaginous phase, an aqueous phase, and an emulsifier composition that includes an ethoxylated alcohol compound and a polyaminated fatty acid compound. The ethoxylated alcohol compound has the formula R.sup.1—(OCH.sub.2CH.sub.2).sub.n—OH, where R.sup.1 is a hydrocarbyl group having from 8 to 22 carbon atoms and n is from 1 to 8. The ethoxylated alcohol compound has a Hydrophilic-Lipophilic Balance (HLB) of less than or equal to 6. The polyaminated fatty acid compound has the formula R.sup.2—CO—NH—CH.sub.2—CH.sub.2—N(COR.sup.2)—CH.sub.2—CH.sub.2—NH—CO—R.sup.3, where R.sup.2 is a hydrocarbyl group having from 1 to 20 carbon atoms and R.sup.3 is a hydrocarbyl group having from 1 to 10 carbon atoms or an alkylene carboxylate group having formula —R.sup.4—COOH, where R.sup.4 is a saturated or unsaturated hydrocarbylene having from 1 to 10 carbon atoms. Methods of drilling wells include operating a drill in a wellbore in the presence of drilling fluid compositions.