METHOD TO CONSTRUCT DEEP WELLS UNDER DIFFICULT GEOLOGICAL CONDITIONS Russian patent published in 2012 - IPC E21B21/14 C09K8/20 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the field of drilling oil and gas vertical and inclined wells under difficult geological conditions. In the method for construction of deep wells under difficult mining and geological conditions with application of thin clay drilling muds of the following composition, wt %: clay 4.0-7.0, carboxymethyl-cellulose 0.5-2.0, sodium or potassium chloride 2.0-15.0, calcium carbonate 3.0-7.0, water - balance; or of the following composition, wt %: clay 4.0-7.0, carboxymethyl cellulose 1.0-3.0, sodium or potassium chloride 2.0-15.0, calcium carbonate 5.0-12.0, water - balance; drilling of geological elements that differ in complexity along a well length is carried out with one composition of a drilling mud, besides, tunnelling of filtering rocks is performed with account of preservation of natural permeability of productive reservoirs, elimination of inflows of a reservoir fluid into a well due to cooldown of a thin clay mud by 15-25°C with simultaneous increase of pressure in it by 3-6% from the mining one.

EFFECT: invention provides for stability of geological elements in tunnelling of wells, prevention of processes of drilling muds (fluids) absorption, inflows of a reservoir fluid, preservation of natural permeability of productive reservoirs by 80-90% from the initial values.