Oil-base Mud to Improve Quality of Pay Penetration
Authors: Deminskaya Nataliya , Molokanov Denis , Sledkov Vladimir , Kuznecov Anatoliy 
Published: September 2014

Abstract
Growth in consumption of hydrocarbon resources in depletion requires effective methods for their extraction. One of these solutions is the construction of horizontal wells, the number of which in recent years have increased exponentially. Since the main task of drilling-horizontal well – is to increase drainage area of depleted reservoirs, the emphasis in this case is also given to the quality of primary formation exposing.
Under the primary formation exposing of the producing formation pressure in the well is usually maintained above the reservoir pressure. As a result, washing liquid and the filtrate has penetrated under the influence of the repression on the producing formation. The dispersion medium of the washing liquid can penetrate into the layer even in the absence of repression by physico-chemical stimulation. Mud and liquid filtrate penetrating into the formation and contaminate collector, impair its reservoir properties in the area adjacent to the wellbore. The main reasons for the deterioration of reservoir properties of this zone – restriction of the pore channels, and even complete blockage of some of them due to mudding of dispersed phase drilling fluid; clay minerals formation swelling upon contact with an aqueous filtrate; upsetting of insoluble sludge in the interaction of the mud and reservoir fluids; reducing the mobility of the formation fluid into the contaminated area. The right choice of mud, subject to the characteristics of the reservoir enable to reduce the level and radius of pollution.
For many decades, it is believed that optimal systems for primary formation exposing are oil-based system. The base of system is a hydrocarbon liquid on physico-chemical properties related hydrocarbon fluid saturating the producing formation. Composition comprises of hydrocarbon fluid, emulsifiers and aqueous phase. Under the influence of differential pressure they are filtered into permeable productive deposits.
Growth in consumption of hydrocarbon resources in depletion requires effective methods for their extraction. One of these solutions is the construction of horizontal wells, the number of which in recent years have increased exponentially. Since the main task of drilling-horizontal well – is to increase drainage area of depleted reservoirs, the emphasis in this case is also given to the quality of primary formation exposing.
Under the primary formation exposing of the producing formation pressure in the well is usually maintained above the reservoir pressure. As a result, washing liquid and the filtrate has penetrated under the influence of the repression on the producing formation. The dispersion medium of the washing liquid can penetrate into the layer even in the absence of repression by physico-chemical stimulation. Mud and liquid filtrate penetrating into the formation and contaminate collector, impair its reservoir properties in the area adjacent to the wellbore. The main reasons for the deterioration of reservoir properties of this zone – restriction of the pore channels, and even complete blockage of some of them due to mudding of dispersed phase drilling fluid; clay minerals formation swelling upon contact with an aqueous filtrate; upsetting of insoluble sludge in the interaction of the mud and reservoir fluids; reducing the mobility of the formation fluid into the contaminated area. The right choice of mud, subject to the characteristics of the reservoir enable to reduce the level and radius of pollution.
For many decades, it is believed that optimal systems for primary formation exposing are oil-based system. The base of system is a hydrocarbon liquid on physico-chemical properties related hydrocarbon fluid saturating the producing formation. Composition comprises of hydrocarbon fluid, emulsifiers and aqueous phase. Under the influence of differential pressure they are filtered into permeable productive deposits.
Components are interact and form a slow-moving mixture which block the pore space bottomhole formation zone.