Papers by Keyword: Gas Drilling

Abstract: In this paper, based on mass conservation, momentum conservation and turbulence k-ε model, the incompressible flow fluid dynamics model in sand discharging process is established. Computational Fluid Dynamics (CFD) technology is adopted to solve the flow field in the bend pipe and the erosion laws of the pipeline wall are predicted coupling material erosion model. Four erosion models of carbon steel material are adopted respectively to calculate the erosion laws and comparison is conducted. Further parametric study is carried out and different influence factors (such as pipeline structure, flow of fluid, et al.) to the erosion laws of the blooie line are discussed. The results indicate that the distribution characteristics of the erosion damage and the law of the erosion rate are changed with impact parameters in the bend pipe. There are obvious distribution differences of the erosion rate within a certain angle range obtained from different erosion models.

Abstract: The paper launched a study of waterproof material for mudstone in gas drilling. The adhesion with rock surfaces and water resistance of four synthetic waterproof materials were experimentally evaluated. The results showed that the four synthetic waterproof materials had a good adhesion to the surface of the rock, which could meet operational requirements in the vertical plane. The synthetic waterproof materials had excellent waterproof property, and could withstand immersion in water of more than 72h.

Abstract: In recent years, the development of super-absorbent material was very fast, its ability to absorb water up to several hundred or even thousands times of its own weight, it provides a new way of gas drilling to solve the water carry problem. According to the characteristic of the formation, we optimized polyacrylic acid salt as the water absorbent material, and evaluate salt resistance, temperature resistance and compression resistance. And we discussed the feasibility and recycling of the technology. And we find that this kind of super-absorbent material which can absorb deionized water 1484 times,absorb 0.9% NaCl aqueous solution 687 times,absorb 50% ethanol 705 times, that can meet the water carrying requirements of gas drilling.

Abstract: Gas drilling technology have very distinct advantages, it can improve ROP greatly, shorten the drilling cycle, reduce drilling costs, but it's scope of application was greatly limited by the problems of formation water and wellbore stability. This project developed a kind of super-absorbent material which can absorb deionized water 1484 times,absorb 0.9% NaCl aqueous solution 687 times,absorb 50% ethanol 705 times, that can meet the water carrying requirements of gas drilling. it provides a new way of gas drilling to solve the water carry problem.

Abstract: 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.

Abstract: For gas drilling, hole cleaning is a particularly critical problem. When the spiral centralizer is used in the down hole assembly of gas drilling, it will produce a powerful rotational flow which will be bond to have the influence of different level on the hole cleaning. For this matter, this paper has established a three-dimensional fluid dynamics model in the basis of gas-solid two-phase turbulent theory and got its numerical solution by using the finite volume method, therefore making a quantitative evaluation about the ability of cutting-carrying and lifting of the spiral centralizer. The results have shown that the spiral centralizer has the function of cutting-carrying and lifting; part of the rock debris pellet concentrates in the bottom of the blade, above less instead. The numerical calculation method has some guiding significance for spiral centralizer design in gas drilling.

Abstract: 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.

Abstract: Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.

Abstract: Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.

Abstract: More cuttings producing in higher penetration rate of gas drilling are usually in the larger non-uniform size at the bottom and in the smaller uniform size back to the wellhead. It is indicating that cuttings in the well should be appeared in the successive breaking in the process of upward migration. According to the particle broken theories, the successive breaking phenomenon were analyzed, and given the calculating method for the probability of secondary impact crushing, and applied the breaking process matrix and the particle size distribution function to the cuttings migration crushing in the whole wellbore. The calculating results show that the cuttings in the wellbore are broken by the uneven size volumetric fracture progressively turned into the surface fracture of the uniform process, and ultimately stabilized the small size distribution.