Fatigue damage in the rotating drill pipe in the horizontal well of mining engineering is usually resulted from cyclic bending stresses caused by the rotation of the pipe especially when it is passing through curved sections or horizontal sections. This paper studies fatigue life prediction method of rotating drill pipe which is considering initial crack in horizontal well of mining engineering. Forman fatigue life prediction model which considering stress ratio is used to predict drill string fatigue life and the corresponding software has been written. The program can be used to calculate the stress of down hole assembly, can predict stress and alternating load in the process of rotating-on bottom. Therefore, establishing buckling string fatigue life prediction model with cracks can be a good reference to both operation and monitor of the drill pipe for mining engineering.

In the drilling process, axial vibration, transverse vibration and torsional vibration happen to drilling string. And the coupled vibration is more complex. In the resonance state, drilling string collides with the wall, which causes serious damage on drilling string in a short time and results in economic loss to the drilling operation. In this paper, the regularity of coupled vibration is analyzed by using finite element method. The model of full-hole drilling strings is established. The distribution regularities of coupled resonant frequency are obtained through computer analysis. The coupled model is more accurate than single vibration model. And the gaps of high rotary speed resonance regions are larger. Resonance state can be avoided by changing rotary speed, and drilling accidents can be reduced.

In gas drilling, hole-cleaning problem is serious due to formation water production when water layer drilled. Drill pipe sticking will affect seriously and drilling work cannot carry out. Therefore, formation water production is the most serious case. In this paper, we research that if formation water production is small, there are two migration model in annulus considering water absorption characteristics of cuttings when formation water production is greater than water absorption. One situation is the migration occurs under the condition that cuttings completely absorb the formation water. Another is cuttings and pure liquid migrate in the form of liquid droplet at the same time when cuttings do not completely absorb formation water. By using the minimum kinetic energy method, we consider the effects of gas influx under the two conditions and find that in most cases liquid carrying need more minimal gas influx than cuttings carrying. When formation water production is small in drilling work, increasing the amount of gas injection should used in order to ensure gas drilling safely and smoothly.

Well deviation control has become a bottleneck restraining the development of gas drilling. Without lubrication of drilling fluid and the existence of negative pressure differential, the reasons of well deviation in gas drilling are different from in mud drilling. The effects of stress distribution difference, rock-breaking mechanism, well bore enlargement and water export on well deviation during both gas drilling and mud drilling are compared and studied on the basis of the previous studies in this paper. The conclusion demonstrates that the new stress state of the bottom rock, the uneven crater which is formed by rock breaking and the borehole enlargement are the main causes of well deviation during gas drilling.

Hydraulic fracture, as a stimulation treatment, has been widely used in process of oil exploring in oil well. But in tight sandstone reservoir, it still exist many problem due to compactness, low-permeability, hardness and brittleness characters of the sandstone. To resolve the problem above-mentioned,this text considering the low natural productivity status of tight sandstone reservoir in Yanji Basin, to analyze the reservoir characters of tight sandstone reservoir base on density testing and mechanic parameters testing of the stone. The results shown that the special reservoir characters of tight sandstone sand lead to high fracture pressure of formation, poor connectivity of fracture, filtration and backflow problems of fracturing fluid. So we put forward reasonable recommendations for fracturing to resolve the problem above-mentioned. Through the application of oriented perforating technology, improvement of fracture fluid system and fracturing technology, provide a new effective technological measure for fracturing in tight sandstone, and promoting the development of fracturing technology in tight sandstone reservoir.