Advanced Materials Research Vols. 594-597

Abstract: Coiled tubing operating systems have complex underground loading, by related research, we have got the solution about actual depth which the coiled tubing goes into well, and we also have got the solution about the buckling and lock-up of coiled tubing. The reasonable overall experiment scheme is put forward according to the related functional requirements, the appropriate geometric parameters and dynamic parameters of the experimental system is determined, the function module analysis and structural design of the test bench is carried on. The experimental phenomena about buckling and helical buckling lock-up are analyzed, and the conditions of helical buckling lock-up are put forward. This experiment has provided the basis for the analysis of mechanical behavior of coiled tubing in wells.

Abstract: Calculation of Short-leg shear walls structural system is a multi-field coupling problem. Through the research and application of short-leg shear wall structure calculation theory, based on the national codes,the short-leg shear wall design principles are established.It is discussed for the reason of the world's first short-leg shear wall structure design formation and development research. According to short-leg shear wall force characteristics, horizonal displacement is divided into destructive story drift and harmless story drift, the formula for calculating the destructive story drift is obtained, using destructive story drift angle parameters and the change of main section height to control the deformation, to control structural rigidity to ensure the structural design rational purpose.

Abstract: In order to improve the development effect of Chang-6 Oil Reservoir, five sets of different production pressure (1MPa, 2MPa, 3MPa, 4MPa, 5MPa) was designed to do CO2 immiscible flooding experiment to analyze the channeling laws. The experimental results showed that gas breakthrough time and gas channeling time were all shortened with the increasing of the pressure difference, but the ultimate recovery had a fluctuation change, increasing first and decreasing afterwards. And the production sharply increased in the gas breakthrough before and after. The best displacement effect was in 3MPa differential pressure. Then plugging experiment was made under the condition of 3MPa differential pressure, isopropyl amine was as plugging channeling agent. The experimental results: the residual resistance coefficient of plugging channeling agent was 8.56, and the range of enhancing recovery efficiency was 15%.

Abstract: Nowadays, in China nearly all the produced oil-fields have already entered the period of high water cut, and the six oil-fields of Daqing and Shengli oil-field etc. have exceeded eighty percent water cut. Beierdong Block has produced for nearly fifty years, and now it has entered into the descending output stage and its water cut has reached more than ninety percent. With oil field infill gradually in Beierdong Block, each series of well network production target getting worse gradually, intersecting with old well network stratigraphic position, and polymer flooding well network use part of water driving old well, making the contradictory of layer well network concatenate and dynamic regulation intensely. Especially as the block of infill adjustment proceeded earliest, acquired better developed effect at the beginning of regulation, but with the deep development of the field, after the phase of extra high water cut, exposed gradually some problems such as the perforating interval is too long, the contradiction of interlamination is obvious, the high water cut of multilayer is serious, bringing huge difficulty to dynamic analysis regulation.Basing on layer recombination and using the reservoir simulation method, the paper studied the distribution of remaining oil, forecast variation regular pattern of development indexes. By contrasting these indexes, the paper estimates the effect of layer recombination. It has important significance for the next period’s development.

Abstract: The permeability and changing characters following variation of physicochemical environment outside of porous media like rock and soil are very important for all kind of civil engineering. But until to now, most theories of them are based on phenomenological method, and they cannot interpret the seepage traits and the variation properties induced by environment changing essentially. The author based on the predecessor’s work which consider that pore number obey exponential and built a capillary bundle model to depict the microscopic peculiarity of porous media seepage. The effect of water temperature, the upper limit of Darcy Law, flow rate beyond Darcy Law’s upper limit, and the infection of porosity on permeability etc issues were discussed theoretically with this model. At last, an instance was calculated with this model for its permeability coefficient and critical hydraulic gradient, and at the end the calculation results were discussed.

Abstract: Separate layer water flooding is adopted in most oilfields in China and the injection flow rate is controlled by the diameter of water nozzle of each layer. In order to ensure the effect of water injection, applicable water nozzles need to be adjusted to meet the requirements of injection flow rate. The adjustment is commonly realized according to experience, which leads to long adjustment time and low efficiency. To solve this problem, the coupling model of wellbore conduit flow, throttled flow and formation seepage was established based on theoretical analysis, which could provide theoretical basis for water nozzles adjustment. In the model, the Bernoulli Equation was adopted to analyze wellbore conduit flow; indoor experiments were done to research throttled flow; the research object of the seepage was finite radius well in homogeneous infinite formation.

Abstract: Base on the non-Darcy flow problem in low permeability reservoirs, the oil-water two phase radial fluid flow model considering threshold pressure gradient is established, the output and formation pressure distribution formulas are obtained，the production variation rule and the influence threshold pressure gradient on formation pressure distribution of different permeability and different well spacing are discussed, the reasonable well spacing of different threshold pressure gradient is calculated. Research shows that, the smaller the permeability, the bigger the corresponding threshold pressure gradient, the faster the production shortfall; in the same permeability, the greater the well spacing, the less the output; the fluid flow requires energy expenditure to overcome threshold pressure gradient, the smaller the permeability, the greater the resistance, the faster the formation pressure descent near wellbore. The reasonable well spacing for effective production is obtained by output formula, which provides the scientific foundation for improving the development effects.

Abstract: In recent years, more and more fractured gas reservoirs were discovered in the world. In general, fractured gas reservoirs are defined as formation with double porosity system, which is composed with fissure and matrix. In reservoirs with double porosity system, only the fissure system are connected with the wellbore and have relatively high permeability, matrix rocks have very low permeability, gas can flow into the wellbore only via fissures, and the flow process be divided into the flow in fissures, transition flow and the flow in the total system. But transition flow is not found in the process of well testing, which results in misapplication of development decision support and selection in gas field development program. In this paper, the influent factors of fractured gas reservoir for estimation are studied by models of single well simulation, and the simulated results are analysis by the method of pressure transient analysis. For example: the time of pressure build-up test, production time, wellbore storage coefficient,kv/kh,the reservoir boundary, the pressure precision, the porosity of matrix and fracture, the permeability of matrix and fracture, the thickness of formation(partial perforation),skin, water saturation etc. The results of simulation show that the disappearance of the transition flow is caused by many factors, which include that the time of pressure build-up test is short, production time is not sufficiently long, ,the vertical permeability is much larger than the horizontal permeability and the formation is perforated partially, the time of the reservoir boundary for pressure is short than the transition flow, the porosity of matrix is close to the porosity of fracture, the permeability of matrix much smaller than the fracture permeability, the pressure precision is low. The transition flow is not affected by the skin, the wellbore storage coefficient and water saturation, which cover up the radial flow in fissure system.

Abstract: Fractured rock masses with many fractures will make the hydro-mechanical characteristics more complex. However, traditional equivalent continuous method just generally reflects the mechanical characteristics for the rocks including large fractures. In order to simulate the mechanical characteristics of the fractured rock masses under complex geotechnical environment, a new method based on Discontinuous Deformation Analysis (DDA) was forward to research on the hydro-mechanical effect. And use the method to analyze the dam foundation, the results compared with that considering non-coupling effect indicated that this model could reflect the hydro-mechanical effect in detail. In addition, FEM and DEM were applied to research on the distribution of the water head, displacement and stress under the same conditions, the results agreed with that by DDA, which further verified the feasibility of the forward method. In addition, the results about the water head and stress analyzed by DDA was greater than that by FEM and DEM, the reason was that this model simultaneously considered the normal deformation and shear deformation of the fractures. Therefore, the forward coupling method based on DDA will provide a research technique for seepage control and stability assessment of the rock engineering.

Abstract: Combining an example of rock slope engineering, the finite element model of excavation, reinforcement with rainfall infiltration conditions is built up. The process of stage excavation and reinforcement of the slope are simulated, and the stress and deformation law and displacement change of the slope during each stage period are analyzed, and the stability of slope is evaluated under some conditions. Moreover, the discontinuous deformatioanalysis model is set up, the limited internal friction angle of the sliding face of slope is obtained, and the slope stability is evaluated. It was shown that the conclusion of two methods was consistent, and the slope was basically stable.