Papers by Author: Hai Yan Zhu

Abstract: Considering the combined action of the fluid penetration and the casing, the seepage coupled deformation finite element model of the highly deviated casing perforation well is established by using the tensile strength failure criterion and applied on the BZ25-1 oil filed. The results show that the increasing of the perforation angle and the well azimuth and the decreasing of the inclination would lead to a higher fracture initiation pressure. The fracture initiation point always locates on the wellbore face when the influence of the casing is considered. When the casing is ignored: when the perforation angle is 0°-45°, the fracture initiation point locates on the root of the tunnel; when the angle is 45°-90°, the fracture initiation point may be on the wellbore face or the perforation biased toward the maximum horizontal stress direction; when the angle is near to 90°, the hydraulic fracturing difficultly fractures the rock through the perforation tunnels. The laboratory hydraulic fracturing simulation experiments of 45° deviated well are carried through 400mm3 cement specimen so as to obtain the fracture initiation point and geometric shape under different perforation angles, the results verify the accuracy of the numerical simulation method.

Abstract: Though statistically analyzing ten typical wells of kelly cock valve failure in certain oilfields, the main failure modes of the kelly cock valve were determined. Aiming at these modes and combining with mechanical analysis of knob, upper seat and main body of the kelly cock valve, its finite element calculation had been implemented and the weakness of all parts was found. By numerical modeling of the flow field of a kelly cock valve it was found that the velocity of fluid rapidly increased at upper and lower valve seats and this could easily prick out ball valves and valve seats, there was a annular low-velocity zone of minimum speed between the ball valve and the inner wall of the main body and this caused solid aggregation at this area. The research in this paper made the modes and causes of kelly failure to be recognized systematically. The results provided theoretical foundations of further improving the design and reasonable using of a kelly cock valve.

Abstract: Percussion drilling has been widely used in oil and gas industry, yet it still has some shortcomings, such as severe damages to drilling tools, low energy transferring efficiency and low rock-fragmenting efficiency. Thus it is necessary to reveal the mechanism of interactions between the hammer bit and rock in geophysical prospecting percussion drilling. Taking account of the coupling effect of the Weight on Bit (WOB), impact force and rotary torque, this paper constructed a Finite Element Method (FEM) model using the finite element analysis software (ANSYS/LS-DYNA) and conducted a computer simulation of bit-rock interaction under rotating and simple impact effect, which showed the rock-fragmenting process of hammer bit and the curves of volume-time and depth-time of craters as well as the effective stress-time curves of the centre tooth, second-row tooth and peripheral tooth. The results showed that: the percussion drilling process under rotating impact effect is characterized as four fundamental processes; the crater depth mainly depends on impact force rather than rotary torque; the crater created under rotating impact effect is twice the volume of that under impact effect; the effective stress of each tooth changes severely: the stress of second-row tooth is the largest, centre tooth the second, and peripheral tooth the smallest. This study provided a guide for the structural optimization of hammer bit and general applications of percussion drilling.

Abstract: To reveal the mechanism of the impactor-bit-rock interaction in geophysical prospecting percussion drilling, considering the coupling effect of the static pressure, impact force and rotary cutting, constructing the physical model of the impactor-bit-rock interaction, and using the finite element methods (FEM), three-dimensional (3D) model of the impactor-bit-rock interaction is established. Using the finite element analysis software (ANSYS/LS-DYNA), the 3D FEM analysis of the impactor-bit-rock interaction is carried out when compressed air pressure is 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa and 1.2 MPa respectively. The results show that: the energy transmission efficiency when piston impacts bit under different air pressure is not high and it should be improved further, bit can not fragment rock until it is impacted by piston, it is found that the best air pressure is 1.0 MPa when the impactor and bit are used to drill granite according to the volume of the fragmented rock and the depth of the crater, the speed and displacement on the radial direction of the piston which should be reduce even eliminate are very harmful. The results are further useful to extend the applications of the geophysical prospecting impactor and hammer bit.

Abstract: This paper uses cellular element method to propose a new calculating method for drill string dynamic model, and applies the calculating method on rigid packed hole assembly model. The results show that, this method has advantages of programming simply, applying boundary condition easily and rapid convergence rate. It is a new method for rigid packed hole assembly optimization design.

Abstract: Based on the failure mode of air hammer bit, a mechanical model of the tooth on the inclined plane is established. And then a new air hammer flat bit with double declined planes and a big central plat (the outer inclined plane is 40° and the inner one is 20°) is designed. In order to reduce the design cost and cut down the design cycle, we establish a 3D contact model of 12 1/4″ full-scale flat bit, teeth and rock to choose a better end face structure from single and double declined planes, verify the rationality of bit parameters and tooth arrangement, design reasonable shrink range between tooth and tooth-Hole. This 3D FEM methodology for air hammer bit design is economical and useful, it can be used to optimize bit structure and design a new bit.

Abstract: In order to reveal the physical mechanism of air hammer drilling process, using the finite element methods (FEM), a three-dimensional (3D) contact model of full-scale bit, full-scale teeth and rock is established by using free meshing method. We use a Mohr-Coulomb type material model to describe when and how rock fails, and a triangular wave to replace the stress wave. Using the finite element analysis software (ANSYS), the 3D contact analysis of the bit, teeth and rock is carried out. The results show that: aggressive tensile failure may be primarily responsible for rock breakage in air hammer drilling, while compressive failure (or shear failure) may only contribute as a minor player; the distribution of the fragmentation dents can be used to verify the rationality of tooth arrangement; the larger tooth-hole stress of the outside rows mainly responses for the bit failure, while the larger tooth stress of the inside rows contributes as a secondary factor. The results are further calibrated with a series of field applications and research results.