Water-based drilling fluid applicable to salt-gypsum layer and preparation method of water-based drilling fluid

Abstract

The invention provides a water-based drilling fluid applicable to a salt-gypsum layer and a preparation method of the water-based drilling fluid. The water-based drilling fluid contains the followingcomponents in percentage by mass: 23.0%-26.0% of sodium chloride, 0.5%-3.0% of a tackifier, 2.0%-15.0% of a filtrate reducer, 1.0%-3.0% of a blocking agent, 0.1%-0.5% of sodium hydroxide, 0.5%-5.0% ofsodium carbonate, 0.1%-0.5% of an ion complexing agent, 2.0%-5.0% of bentonite powder, 5%-30% of barite and the balance of water. The prepared water-based drilling fluid has excellent inhibition property and anti-sloughing property to the salt-gypsum layer, so that the technical problems of wellbore instability, recurrence loss type well leakage and the like caused due to the dissolving and creepage of a large section of the salt-gypsum layer and the collapse of salt rocks are effectively solved. The water-based drilling fluid is successfully applied to Ordovician, Cambrian and Changchengianstratums in Ordos Basin and can meet the demands on deep unconventional exploration and development of oil and gas reservoirs in Ordos Basin.

Description

technical field [0001] The invention relates to a water-based drilling fluid suitable for salt-gypsum layers and a preparation method thereof, which have excellent inhibition and anti-slump performance on the salt-gypsum layers, and effectively solve the problems caused by the dissolution and creep of large sections of salt-gypsum layers and the collapse of salt rocks. technical problems such as wall stability and loss of return lost circulation. It has been successfully applied in the exploration and development of Ordovician, Cambrian and Changchengian formations in the Ordos Basin. Background technique [0002] With the large-scale development of unconventional gas reservoirs at home and abroad, the drilling of deep complex oil and gas resources is becoming more and more extensive. Taking the Ordos Basin as an example, the layers drilled and exploited in the past were all strata above the Ordovician. Because the Ordovician and its lower Cambrian and Changchengian strata...

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Problems solved by technology

[0010] In order to overcome the problems of dissolution and creep of salt layers, water absorption and swelling of anhydrite, mudstone expansion and dispersion, slurry collapse, plugging of drilling fluid, and anti-calcium ion pollution, the present invention provides a water-based drilling fluid suitable for salt-gypsum layers and its preparation method, one of the purposes of the present invention is to have excellent inhibition and anti-slump performance on the salt-gypsum layer, and effectively solve the problem of well wall stability and loss of return lost circulation caused by dissolution creep of large-section salt-gypsum layer and salt rock collapse. and other technical problems

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