Xiao Zeng Wang

Development of the Ring Block Drill Pipe Casing Wear Tester and Experimental Research

In deep wells and ultra-deep wells the complex geological conditions often result in serious casing wear. In order to be able to accurately measure the wear efficiency and friction coefficient required in the process of the prediction of casing wear, a ring-block drill pipe and casing wear tester is specifically designed and produced, the scheme of tester is proposed, and the design of structure, driving device, and the detecting system of the friction and contact forces of tester is completed. Adopting the ring block drill pipe casing wear tester and simulating down hole conditions P110 casing wear experiments are finished. The results show that the ring block drill pipe casing wear tester meets the requirement of down hole casing wear experiment. P110 casing wear efficiency decreased with the increasing of wear time. The friction coefficient between the P110 casing and the drill pipe sample is about 0.25.

Study of Resistance to Wear of P110 Casing Down-Hole in Water Based Mud

The operation of drilling well leads to casing wear to some degree in cased well. The reduced strength of worn casing threats to the safety of well test and completion. In order to calculate casing wear depth and prevent the casing wear, the wear efficiency and friction coefficient is measured in the different wear time, the contact force and the rotating speed. The wear efficiency increases with the contact force and the rotating speed. And the bigger the rotating speed, the bigger the friction coefficient. The wear efficiency of P110 casing is change from 2 to 8×10-13 1/Pa. The rotating speed has less influence on the wear efficient. So it is reasonable that the wear efficiency model is adopted to calculate the wear degree of P110 casing.

Casing Wear Influence Factors and Range Analysis

In the deep and ultra deep well casing wear is serious. The decrease of strength leads to casing damage, affects the follow-up well test and completion. In order to analyze the influence of the contact force, rotating speed, steel grade and muds on casing wear, determine the optimized level collocation scheme which makes casing wear minimum, optimize drilling parameters and casing programs, reduce casing wear, four factors and three levels orthogonal experiment of casing wear was carried out, and the range analysis of the experiment results is made. The results show that the best match of factors is A1B1C1D3, namely when the contact force is 200 N(A1), rotating speed 60 r/min (B1), steel grade N80(C1), oil-based mud (D3) casing wear is minimal. The influence of muds on casing wear is the largest, the next is casing steel grade, and then rotating speed, the effect of the contact force minimal. The improvement of mud performance is best method to reduce casing wear.

Measurement of Temperature Resistance of High Power LED

In the absence of cooling measures, the chip temperature of high power LED rises rapidly. When the junction temperature exceeds the maximum allowable temperature, the high power LED will be damaged due to overheating. In the design of high power LED lamps, the main work is to the temperature design. Using a good linear relationship characteristic of the semiconductor devices between the LED junction voltage and junction temperature, this paper measured the high-power LED working voltage, working current, temperature of the incubator and heat sink. Adopting the method of electrical parameters, the paper measure the temperature resistor of high power LED. The high-power LED temperature resistance measuring instrument is designed and made. The temperature resistance from the LED wafer to the heat sink is measured fast and accurately, and the error is less than 5%.

Influence of Rolling Bearing Steel Ball Temperature Deformation on Radial Clearance

According to theory of thermoelasticity, the paper deduces the formulas of the rolling bearing steel ball transient temperature, radial stress, tangential stress, radial displacement, and radial clearance, analyzes the influence of the temperature deformation on the radial clearance. The result shows that the radial displacement changes slowly on the surface, reaches the maximum when temperature becomes stable. The reduction value of the radial clearance is the linear function of the temperature and position. Fitness formula is adopted to calculate the radial clearance in the different temperature and radius. The error is less than 0.2% and 0.18%. The radial clearance formula is used to calculate the bearing’s maximum working temperature when the radial clearance reaches the standard radial clearance to ensure the reliable work of the bearing.

Influence of Hardness on Casing Wear Resistance in Polysulfide Water Based Drilling Fluid

Worn casing often appears in deep and ultra deep well which effected by many factors in drilling process, such as casing grades, drilling fluid density and contact forces, and so on. Using polysulfide water-based drilling fluid, simulating the actual bit pressure, rotary speed and other influencing factors, the wear experiments of TP140,VM140,P110 and N80 casing which often are adopted in the oilfield are completed, and the wear efficiency and friction coefficient which are adopted to predict down hole casing wear are obtained. The experimental results show that the higher casing steel grade, the greater the hardness, the better wear performance. The experiments can help deepen the understanding of the mechanism of casing wear. Adopting the results which are obtained in research the prediction accuracy of down hole casing wear can be improved.

Influence of Geometrical and Physical Parameters of Cement on Loads of Casing and Cement

A mechanical model of casing, formation and cement is established under the action of the in-situ stress in the cementing section. According to the continuous displacement and radial stress conditions, the calculation formulas of loads applied to casing and cement are developed. The influences of geometrical and physical parameters of cement on loads and stresses of the casing and cement are analyzed. The result shows that the increase of Young’s modulus of cement results in that the casing load increases firstly, and then decreases. The bigger Young’s modulus of cement, the more load of cement. Along with the increase of Poissons ratio of cement, cement and casing load become bigger. Cement load is greater than the casing one, so it can avoid damaging casing.

Analytic and Numerical Solutions of Load and Stress of Casing and Cement in Cementing Section

With the prolonged production term and the stimulation of the oil well in oil-field, the load which results from the in-situ stress is one of the main reasons to the casing damage. Taking the casing in Cementing section, the cement and the rock surrounding the cement into consideration, a mechanical model is established, while analytical solutions of displacement and stress distribution is obtained. The finite element method is adopted to obtain the numerical solutions of the mechanics model. The result shows that analytical solutions and finite element solutions are approximate. Finite element model of casing/cement/formation which is established in the paper can be used to analyze the load and stress distribution of worn casing with non-uniform in-situ stress.

Experiment Research on Influence of Mud Density to Wear Resistance of TP140 Casing

Due to complex down-hole conditions and longer drilling time, there are serious casing wear in deep and ultra deep well. It is necessary to carry out a deeper research of the casing wear. Theory of casing wear and prediction method are not perfect in deep well and ultra deep well .The purpose of this paper is to obtain the wear efficiency and friction coefficient which is used to predict wear of the TP140 casing in down hole. A block-ring casing wear tester is specially designed and produced. The wear efficiency and coefficient of friction which is used to predict wear of TP140 casing in different density polysulfide water-based mud is obtained. The influence of the mud density on the TP140 casing wear resistance is analyzed. It is found that the larger mud density, the bigger casing wear efficiency and the friction coefficient.

An Analysis of the Collapse Strength of Down-Hole Tubings Loaded by Axial Compressive Forces and Bending Moment

Due to collapses of tubings during well testing and completing in HPHT wells, it is required by Petrochina officially to calculate and analysis the collapse strength of down hole tubings with axial forces and corresponding bending moment being taken into considerations. Based on the 4th strength theorem, formulas were derived and method was present to analyze the collapse strength of down hole tubings loaded by compressive axial forces and bending moment to fulfill the official requirements, which could not be accomplished according to published standards and references. And, influences of axial tensile forces, compressive forces and bending loads on the collapse strengths of down hole tubings were studied. It is found that the collapse strength of down hole tubing loaded by compressive axial force is smaller with compressive axial force and buckling bending moment taking into considerations. The bigger the compressive axial forces, the smaller the collapse strengths.