Hydrocarbon-based drilling fluid

FIELD: oil and gas production.

SUBSTANCE: invention provides environmentally safe hydrocarbon-based drilling fluid suitable for use during boring and completion of oil and gas wells. Drilling fluid is characterized by required viscosity and structural properties within a wide water content range and, in particular, contains, wt %: castor oil 50.0-83.0, colophony calcium resinate (thickener) 4.0, calcium chloride 10.0, Neonol AF-9/12 (emulsifier) 0-0.3, organophilic bentonite 2.0-3.0, water 0-30.0, and penosoline (waterproofing agent) 0-20.

EFFECT: improved environmental condition.

2 cl, 2 tbl

The invention relates to the drilling and completion of oil and gas wells.

In the world more and more widespread during drilling, and especially when completions are oil-based solutions (ROUAULT). There are two class ROUAULT: anhydrous hydrocarbon solutions (lime-bitumen solution and gelled oil) and hydrophobic-emulsion drilling muds (GER) with a high content of the aqueous phase (see Aijalon, Agulation. Reference drilling engineer in two volumes. M.: Nedra, 1985, volume 1, page 360; Vieques, Ibhayi. Hydrophobic-emulsion drilling muds. M.: Nedra, 1983 equivalents).

The main problem with drilling fluids oil-based (ROUAULT) is their potential negative impact on the environment, particularly in sensitive areas (marine, floodplains). Particularly acute this problem is reinforced by the trend towards stricter requirements for environmental protection around the world.

The problem of reducing toxicity ROUAULT was raised abroad in the late 70-ies of XX century and its solution is connected with the use of hydrocarbon liquids under the joint name of "mineral oil". However, the use of mineral oils did not solve the problem of ecological safety of ROUAULT. Biological degradability Rast the Directors based on them does not exceed 5 %, it is not possible to remove restrictions on their discharge into the sea.

In this regard, it was suggested that the problem of creating biodegradable drilling fluids to synthetic non-aqueous-based alternative ROUAULT and with all their merits.

Known emulsion drilling fluid containing castor oil, non-polluting, which is a direct emulsion system, the basis of this mud is a complex gel, biodegradable in aerobic and anaerobic conditions, containing non-polar dispersion medium, the liquid polymeric surfactant surfactant in acid form, are dissolved or dispersed in a specified non-polar environment, agent for neutralization of the polymeric surfactant containing from 0.2 to 5 molecules of water per molecule of surfactant, emulsifier and/or solid filler, soluble or insoluble in non-polar environment.

The gel is used to prepare the drilling fluid is water-based (see U.S. Pat. U.S. No. 5858928 And, From 09 To 7/02, 112.01.1999, PROTOTYPE).

The disadvantage of this technical solution is the fact that the very hydrophobic (nonpolar) gel as a flushing fluid (according to the US patent 5858928 And, From 09 To 7/02) is not used, and made of it the drilling fluid is water, i.e. it basically contains from 97 to 99,09% water. Therefore, the I et to its high water retention capacity f=18-20 cm ³/30 min API released moisture can be hydrated and resiprocate water-sensitive rocks that comprise the walls of the wells, as well as cause swelling clay part of the skeleton, oil formation, which leads to lower productivity or complete blockage.

The technical result of the invention is to provide an environmentally safe drilling fluid hydrocarbon-based (ROUAULT) with the desired viscosity and structural performance in a wide range of water contents by applying a new widely available hydrocarbon framework.

Drilling mud containing castor oil, emulsifier, calcium chloride, bentonite and water, contains organophilic bentonite, as an emulsifier - neonol AF-9/12, and optional thickener is calcium resinate rosin in the following ratio, wt.%:

The drilling fluid may further comprise a wetting agent - benazolin 0 - 2.0 wt.%.

evocomnet stated components in the claimed proportions provides such an inverse emulsion which during drilling, being filtered in the rocks, not causes swelling and, consequently, their softening. And at the opening of oil and gas reservoir of the inventive drilling fluid does not cause swelling clay part of his skeleton, which allows full preservation of reservoir properties of productive formation.

In laboratory studies were prepared samples ROUAULT both classes - solution not containing aqueous phase and a hydrophobic-emulsion drilling muds (GER) with minimum (10%) and 30%content of the aqueous phase.

Samples ROUAULT was prepared according to the methods and techniques described in the papers, "Hydrophobic-emulsion drilling muds", Vieques, Ibehavior. - M.: Nedra, 1983, "the Use of inverse emulsions in oil production", Haarlow, Mscode, Wampool. - M.: Nedra, 1991

Was used for research methods and apparatus according to RD 39-2-645-81 "Method of monitoring parameters of drilling fluids", Krasnodar: Unicraft, 1981

The results of studies of oil-based solutions (ROUAULT) on the proposed technical solution is presented in tables 1 and 2.

This technical result is achieved for any values of the specified interval, for example, drilling mud contains, in wt.%: castor oil 80, calcium resinate rosin 4,0, calcium chloride 10,0, neonol AF-9/12 0,1, organophilic bentonite 2,5, water 3,3, benazolin 0.1 or castor oil 60, calcium resinate rosin 4,0 calcium chloride 10,0, neonol AF-9/12 0,25, organophilic bentonite 2, water 23,6, benazolin 0,15.

According to the experimental data given in tables 1 and 2, solutions (ROUAULT) on the basis of castor oil have technological options to meet all the requirements of the drilling operations. Their rheological characteristics have relatively low values. So effective viscosity (see table 2) in all three types of solutions n is located within 60-70 MPa· s, which corresponds to values of almost viscosity of the fluids used oil-based. The values of plastic viscosity in the range 68-50 mPas, solutions based on castor oil, almost identical values of solutions of oil-based. Dynamic shear stress in the range of 19 to 20 DPA at the proposed solutions consistent with the values of classical ROUAULT oil-based and provides them a safe carrying capacity. Rate hot filtration (f₉₀in the range of 1.27-19,17 cm³30 minutes allows solutions castor oil having a low loss solution in the circulation process in downhole conditions and the magnitude corresponds to the classical ROUAULT. With regard to these indicators (proposed solutions), as Gliniasty, stability, electrocapillary, the values characterize the proposed liquid as extremely stable (see table 2). Thermal stability of the proposed systems corresponds to 120°C.

It should be noted as a positive quality of their high inhibitory ability (P₀=0,187 cm/h) and low surface tension of their filtrates (σ=6,52-7,82 μN/m), which determines the qualitative completion and high flow rates of extracted raw materials.

In addition, the proposed drilling muds OS is ove castor oil are absolutely environmentally safe and can be used in the drilling of offshore oil and gas, so as allow the disposal of waste drilling fluids directly into the waters without damage to the environment. Because the basis (castor oil) and the thickener are biodegradable and fully utilized by microorganisms from the environment.

Thus, the task of the present invention is solved by thickening of castor oil calcium resinatum rosin and creating invert (reverse) emulsions based on it.

1. Drilling mud containing castor oil, emulsifier, calcium chloride, bentonite and water, characterized in that it contains organophilic bentonite, as an emulsifier - neonol AF-9/12 and optionally a thickener is calcium resinate rosin in the following ratio, wt.%:

2. Drilling mud under item 1, characterized in that it additionally contains a wetting agent benazolin - 0 - 2.0 wt.%.