Synthesis and characterization of organic bentonite using oglanly clay: application as viscosifier in oil drilling fluid

A drilling fluid is defined as a circulating fluid used in rotary drilling to perform any or all of the various functions required in drilling operations. Drilling fluids are mixtures of natural and synthetic chemical compounds used to cool and lubricate the drill bit, clean the hole bottom, carry cuttings to the surface, control formation pressures, and improve the function of the drill string and tools in the hole. They are divided into two general types: water-based drilling muds (WBMs) and oil-based drilling muds (OBMs). The type of fluid base used depends on drilling and formation needs, as well as the requirements for disposition of the fluid after it is no longer needed. Drilling muds are a special class of drilling fluids used to drill most deep wells. Mud refers to the thick consistency of the formulation. bentonite organobentonite drilling fluid

This study aims at obtaining an organophilized bentonite into oil-based drilling fluid. Developed-Oglanly organoclays can be used for the first time as viscosifiers in diesel-oil drilling fluid.

2. Experimental

2.1 Materials

Natural bentonite sample was collected from Oglanly deposit of Balkan district of Turkmenistan. This bentonite modified with quaternary ammonium salt-CTAC (brand: Hammadde sebeti CTAC 29 Cetrimonium chloride; molecular weight: 320 g/mol). Organobentonite polyoleogel and konfigel were used for comparison purposes from НПО “ПОЛИЦЕЛЛ”. The composition of this organobentonite b y mass is 7085% of montmorillonite, 15-30% of quaternary salts. In order to purify the crude clay, the powder was firstly treated with dilute HCl to remove carbonate ions, washed with distilled water until cleared from chloride ions (negative test with AgNO₃). The product was dried at 120°C, milled and sieved. The chemical composition of purified clay was analyzed.

2.2 Chemical composition of bentonite clay

The mineral composition of bentonite clay obtained from the Oglanly mine of the Balkan velayat was analyzed, and as a result, it was found that its main component consists of the mineral montmorillonite and is suitable for the production of organobentonite. That is, 65-80% by weight of the montmorillonite mineral is considered suitable for preparing an organophilic clays. The montmorillonite mineral content of 73% in the bentonite core of the Oglanly mine is shown in Table 2. The chemical composition of the local raw material was investigated and studied in an X - ray diffraction analyzer.

2.3 Preparation of organoclays

The purified bentonite sample was modified with quaternary ammonium salt- CTAC 29 Cetrimonium chloride purchased from Hammadde sebeti 5 gr of purified bentonite homogenized with 3gr of quaternary ammonium salt-CTAC in a 100 ml 50% solution of isopropanol. This suspension was stirred for 1hr at 80-90°C temperature.

Then the suspension was filtered and several times washed with distilled water to remove excess of chlorine ions. The modified sample was dried at 90-110^oC temperature for 8 hr.

2.4. Analysis of the obtained clay for compatibility with organophilic clays

The obtained clay sample was tested for organophilic clays in the drilling mud laboratory of the Natural Gas Research Institute. The finished clay is light ash on the surface. It was compared with configel clays.

Configel is white ash with a yellowish tinge in appearance. It is used to increase the viscosity of hydrocarbon-based liquids and to form a crust on the well wall.

2.5 Preparation of oil drilling fluid. Rheological and physical studies.

First, a hydrocarbon-based mud was prepared. For this purpose, the calculated chemical weights were weighed on laboratory scales (Table 1). Then, using a laboratory mixer, the solution was prepared and the rheological parameters of the solution were determined using laboratory equipment, namely:

1. Density of the solution according to a special scale or aerometer;

2. Measure the viscosity of the solution on a beaker-type viscometer VBR-1;

3. Rheology of the solution in the rotary viscometer V SN-3;

4. Solution watering in the WM-6 apparatus;

5. Measure the amount of hydrogen ions (pH) of the solution with an indicator wetted in paper wipes;

6. Heat the solution in the SNOL electric furnace;

Amount of chemicals required to prepare oil-based drilling mud.

Table 1.

The chemicals listed in Table 1 were thoroughly mixed with a mixer. The basic parameters of the prepared oil-based drilling mud were tested. The solution was then heated in a SNOL electric furnace for 6 hours at + 150 ° C. After that, the solution was pre-cooled to room temperature and thoroughly mixed in a laboratory mixer for 10 minutes. Then, all the mud parameters were re-checked.

In this study, the Oglanly deposit's organobentonite was successfully prepared by an intercalation of cationic surfactant CTAC by exchanging reactions and testing the use as a viscosifier in oil drilling fluid. From interpreted results thus Oglanly's organobentonite can be used as a good viscosifier is the diesel oil drilling fluid with higher rheological properties.

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