Advanced Materials Research Vol. 868

Abstract: Threshold pressure gradient for extra-low permeability reservoir is studied experimentally. A production model is established which couples wellbore pipe flow, fracture linear flow and reservoir non-Darcy flow. The influence of bottom-hole pressure and reservoir permeability on threshold distance is performed based on the model. A fracture spacing design method is provided for different bottom-hole pressure and reservoir permeability. Results show that threshold pressure gradient increases considerably as permeability decreases when permeability is below 0.02 mD; threshold pressure gradient is relatively lower when permeability is greater than 0.1 mD; threshold pressure gradient decreases gradually and flattens when permeability lies between 0.02 mD and 0.1 mD. Simulated threshold pressure gradient of formation water is as one-third as that of crude oil. While permeability is between 0.01-0.05 mD, 0.05-0.1 mD, 0.1-0.5 mD and 0.5-1.0 mD, the optimal fracture spacing is about 9 m, 16 m; 36 m and 50 m.

Abstract: Sebei gas field is featured with the characteristics of the shallow-buried gas reservoir, long gas containing well section, multilayer gas reservoirs beds, the complicated gas/water contact distribution, the water produced obviously, sands produced frequently from the gas wells and the multi-layers gas reservoir extracted unbalancedly in the developing process. For these reasons, the paper proposed the method that interlayer interference coefficients are defined with statistical function. Combined with the data of the sand-layers profile test, the effects of the numbers of different sand-lays, the perforated thickness, the perforated interval length and permeability contrast on the interlayer interference are evaluated and these permeability parameters are optimized.

Abstract: In order to study the flow field characteristics around perforating well eyeholes, using the finite element method, it utilize actual physical property, establish the geometric model, through the grid partition and post-processing, got the velocity field and pressure field cloud chart, and analysis the data of controlled, got the mobility pattern of the flow field of around eyeholes. Through three of different eyehole deep using the same physical parameters for modeling analysis, the influence of different eyehole depth of flow field around the holes is got. Through the contrast simulated results of perforating completion heat flow model with the exact solution of open hole completion, the result reveals the specialty and the regular pattern of perforating completion flow field. Meanwhile, according to the theory of water and electricity similar, the actual physical model of perforating completion electric analogue is made and actual the pressure field distribution around eyeholes is measured. The results agree with the results of ANSYS heat flow field simulation. This verify the correctness of the ANSYS analysis. Research shows that using heat flow field module of ANSYS simulation seepage field to serve research seepage field of well is a kind of general method.

Abstract: Large-diameter annulus and conventional annulus are very different in hydraulic property. Based on numerical simulation, a study on pressure loss of large-diameter annulus was carried out. The influence of annular velocity, pipes rotation speed, mud property and annular diameter of marine riser segment on pressure loss was also analyzed and compared with that of conventional segment. The results show that under the condition of large-diameter annulus, the pressure loss of power law fluid laminar flow decreases with the increase of the rotational speed of drill pipe and the contrary tendency occurred when it is turbulent flow. With the increase of the flow behavior index and consistency coefficient, annular pressure loss increases exponentially and linearly respectively. From an overall perspective, with the increase of annular size, the annular pressure loss sharply reduced, and it has great effect on pressure loss.

Abstract: In order to study the near wellbore area of perforated well and after adsorption detention flow variation of rheological property of polymer solution , artificial physics and artificial cylindrical core model 1:10 are used to do experiments. Results indicate that natural degradation processes of polymer solutions, it is plummeting rapidly within 20 day, then reach stability. Near bore the constant speed when the polymer injection and a variable speed injection, the decreasing amplitude of apparent viscosity caused by the shear factor is approximately 22.5%. In the process of adsorption and detain, injecting 0.8pv polymer, model began to produce polymer. About injecting 2.6pv , adsorption and detain reach stability.

Abstract: As concerning the limitations of the classic capillary number theory in the applications to the oil displacement with the ultra low interfacial intension system in low permeability reservoirs, considering the flow velocity of water/oil displacement through pores in low permeability reservoirs and the mechanism of displacement of the remaining oil in the parallel pores, and considering the influences of ultra low interfacial intension on oil/water relative permeability and the influences of non-homogeneity on the recovery, the expression of modification of the capillary number was given. The relation curves of recovery and capillary number were plotted through the displacement experiments with the ultra low interfacial intension system in low permeability cores. Some points on the application of capillary number to the oil displacement with the ultra low interfacial tension system were given, and the reasonable ways of enhancing the recovery of water flooding low permeability reservoirs with ultra low interfacial intension system were shown.

Abstract: Seismic invention is a key technique of concealed reservoir exploration. Stochastic seismic invention with multi-well bound combined with cross-borehole seismic data by striking probability density function of logging data to achieve reservior forecasting. They had the advantage of the higher vertical resolution, and were not fully controlled by the distribution of wells. The results of stochastic seismic invention could be impedance, or other reservoir parameters, and they reflected the physical properties of rock more directly. Analysis indicated that it could acquire high precision reservoir prediction by using the method.

Abstract: The fractured low permeability reservoirs develop complex fracture network. As the of waterflooding recovery heightens, excessive high injection pressures and excessive water injection rate will result in open, initiation, propagation and coalescence of micro-fracture, connecting injection with production form the high permeability zone, which results in a one-way onrush of waterflooding, water cut in oil well water rise quickly, causing a severe oil well flooding and channeling, thereby reducing the ultimate oil recovery efficiency. The effect of the waterflooding seepage within natural fracture on fracture initiation is studied and analyzed here, applying the theory of rock fracture mechanics to analyze the interaction of fracture system for naturally fractured reservoirs in waterflooding developing process, studying the mechanical mechanism of opening, initiation, propagation and coalescence of natural fracture under injection pressure, which is important theoretical significance for studying the distribution law of fracture and defining appreciate water injection mode and injection pressure in the process of injection development of the naturally fractured reservoir and for delaying the directivity water break-through and water flooding rate of oil well in the process of injection development.

Abstract: With the advances in biological sciences, microbiology techniques to be applied to people in all areas of production and life, this paper introduces the microorganisms in the oil industry in all sectors such as oil and gas exploration microorganisms, microbial enhanced oil recovery and microbial degradation of the oil pollution and other aspects of the application. By summarizing the impact of microbial technology for the various aspects of oil industry, make the foundation of the microbial creative application in the field of oil industry.

Abstract: Petrophysical property cutoff effective reservoir properties can be affected by reservoir properties, crude property, depth, formation temperature, formation pressure and other factors, among which reservoir properties, burial depth and formation temperature are the main factors in effective reservoir development degree of deep tight sandstone, formation pressure has a great impact on the effective reservoir development, while fluid properties have a relatively small impact. The development of oil production technology would reduce petrophysical property cutoff, which will lead to the transformation of non-effective reservoir earlier reckoned into effective reservoir in the future. Therefore, it is necessary in oil and gas exploration to continuously analyze lower limit of effective reservoir physical properties.