The consecutive life of the positive displacement motor depends on its main shaft bearing assembly,but the assembly is a weak point.

During directional drilling in the coal mine engineering hole ,the lateral force on bit is one of major mechanical properties of the positive displacement motor assembly (PDM), which includes the bent sub-positive displacement motor assembly (BS-PDM) and the bent housing-positive displacement motor assembly (BH-PDM).

In oil drilling engineering, the workers play much attention on how to increase the rate of penetration during controlling deviation of vertical well The structure of drill-assembly, which uses single bend PDM (positive displacement motor) to control hole deviation, is presented in this paper.

Study on the rubber stator compoundof one step injection screw drilling tool;

Design of the hydraulic testing platform for screw drilling tool;

A computer aided test (CAT) system for testing the performance of screw drilling tools and screw drilling motors are developed.

To meet the demand of higher built-up rate,single-bending screw drill tool with large angle is used during the drilling of the moderate-and short-radius horizontal well.

The downhole milling pipe string of screw drill tool will produce great reverse torque while milling and grinding the bridge plug, cement plug and so on, and which is extremely harmful to the screw drill tool.

The operation performance of PDC bits with screw drill tool appplied now in oilfield were analyzed comprehensively.

Analysis of structural improvement of flexible shaft of screw drill;

Development and application of test bed for large torque screw drill;

Investigation in WC-Co coating of detonation spraying and its application on screw drills;

BULIT-UP RATE AND PDM'S STRESS ANALYSIS FOR MEDIUM- AND SHORT-RADIUS HORIZONTAL WELLS;

DESIGN AND PERFORMANCE ANALYSIS FOR EQUIDISTANT LINING OF PDM;

PERFORMANCE ANALYSIS FOR UNIFORM WALL THICKNESS BUSHING OF PDM;