METHOD OF MUD FLUSH SELECTING FOR CONSTRUCTION OF INCLINED AND HORIZONTAL WELLS TROUBLED IN UNSTABLE ARGILLACEOUS DEPOSITS Russian patent published in 2017 - IPC E21B21/01 

FIELD: mining.

SUBSTANCE: during the method implementation, a hole stability geomechanical model is constructed on wells drilled at the field by setting vertical intensity, pore pressure, minimum and maximum horizontal intensity and their orientation, strength and elastic properties of rocks. Next, the stability calculation of the design well is performed and a "safe window" of mud flush density is established, including an equivalent circulation density. Then, a uniaxial compression test of core samples of a previously drilled well in this field in the initial state, as well as in a mud flush medium of various compositions, but included under the previously defined "safe window" density, with the coefficient of softening and bond value reduction degree in matrix of rock. The hydraulic calculation of the well washing process is performed taking into account the well design and the cavernometry; characteristics of the bottomhole assembly, well trajectory, pore pressure and fracture pressure; geothermal gradient; elastic properties of rocks, speed of tool movement in the wellbore; rheological parameters. The choice of mud flush is carried out on the basis of two conditions: the solution ensures the preservation of core samples strength properties at the level of the initial state, as well as its plastic viscosity and dynamic shear stress do not exceed the maximum values.

EFFECT: increased accuracy of mud flush selection.

2 cl, 5 tbl