Advanced Materials Research Vols. 1073-1076

Abstract: In S Development Area, the production targets of each well net went bad and had interleaved distributions with old well patterns. Meanwhile, polymer flooding well patterns made the conflict of cohesion and dynamic regulation outstanding. Especially, Bei block, first using infill drilling modification, however, had troubles in extra high water period, such as long section of perforation, obvious inconsistencies between formations and high water of layers, which brought difficulties to dynamically adjusting. We selected 1.30 km² west blocks in Bei block, made tests about sediment group restructuring to improve water flooding development effect, redistributed the series of strata and redistributed the flooding network according to the characteristics of development between the layers, combined comprehensive consideration with follow-up adjustment, such as primary network, injection production system and typed II reservoir the tertiary oil production, optimized the layers combination and well patterns arrangement, finally formed technical ideas of high water cut layers adjustment and well nets evolution.

Abstract: Experiment study on shallow gassy unsaturated sand under different confining pressure with GDS triaxial system's 4D stress path module is carried out. Different SWCC shapes under different confining pressures are analyzed. The results show that unsaturated sand's water retention capacity declines gradually with confining pressure infliction and accretion. Finally, shallow gassy sand's gas reservoir pressure characteristics with SWCC are analyzed and forecast, and it's conservative if the same thing is done based on SWCC without confining pressure.

Abstract: Tight oil can be commercially recovered by horizontal well multistage fracturing. With the development of multistage fracturing tools, extended reach horizontal well could be a way to enhance unconventional tight oil economical efficiency. On the base of the study on Cardium formation, fracturing fluids were analyzed and slick water fracturing fluid was optimized. Frac port multistage fracturing string was studied and applied in pilot tests. Three extended reach horizontal wells with average 40 stages and 2954m horizontal length pilot tests were applied and studied. Comparison of well costs and production between extended reach horizontal wells and offset short horizontal wells were studied, extended horizontal reach wells get much more profits after six months producing when oil price above 101 CAD/bbl, and save 50% well construction costs and producing management costs.

Abstract: In order to study the regularity of shear degradation of polymer solution, the artificial core is used to simulate the flow of polymer formation^[1]. The influence of mass concentration, molecular weight and shear rate on the rheological of polymer solution is studied. And the stability of the polymer solution after degradation were analyzed through method of indoor simulation experiment Research shows that Polymer solution is degraded after shearing , the viscosity reduced and it will not rebound with the passage of time. When the solution was sheared through the porous medium, degradation rate increases with the increase of shear rate. Also it can be seen, in the case of the same concentration, the degradation rate increases with the increase of relative molecular mass. In the case of the same relative molecular mass, the degradation rate increases with the increase of the mass concentration.

Abstract: The crude oil of H oilfield contains wax and asphaltenes, and the formation water salinity is up to 160000-220000mg/l, so there is a tendency that the asphaltenes and scale will be deposited in the wellbore during the course of well production, which will influence the normal production greatly. It is necessary to make clear the sedimentary law and corresponding measures. The content of organic and inorganic of wellbore deposits of H oilfield is analyzed through a series of laboratory tests. On the base of the test results, integrated with comparison of conventional deposit prevention and removal technologies, chemical and mechanical methods are recommended. Moreover, formulation of the acid cleaning agent is determined and the principle and process of mechanical removal method is presented.

Abstract: The contact and slide under high pressure between casing and tool joint leads to wear of the casing inner surface in cemented well. The reduced collapse and burst strength of worn casing threats to the safety of oil and gas well. In order to calculate the wear depth and residual strength of 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 is in proportion to the contact force and the rotating speed. The wear efficiency of P110 casing change from 2 to 4×10^-13 1/Pa. Friction coefficient reaches maximum value under certain contact force and rotating speed. The rotating speed has less influence on the wear mechanism of casing, while the contact force play a greater influence on the wear mechanism.

Abstract: The decrease of strength leads to damage of worn casing under non-uniform loading, affects the subsequent well testing and completion. In order to verify the finite element model of hoop stress of eccentric worn casing, unworn and worn casings are crushed under the concentrated force, while the critical concentration force and hoop stress are measured. Under the concentrated force, The difference between the numerical solution of hoop stress of eccentric worn casing and the experimental value is from 3.5% to 5% at outer surface of worn position. The established finite element analysis model of casing hoop stress and derived formula can be used to calculate the hoop stress of unworn casing. It is feasible that the finite element method is adopted to analyze the eccentric worn casing hoop stress.

Abstract: During the development of the oilfield, the water cut of the water controlled field is an aggregative indicator which is affected by various factors. It can reflect the restriction of liquid flowing rules from the oil layer and crude oil physical property, and the effect of serious technical measures during the exploitation. Water cut increasing rate is closely related with water cut. The level of water-cut increasing rate of various well network was evaluated during oil producing with extra-high water cut in Xingnan development area, compared the differences among various well networks, and analyzed the geology causes and development causes.

Abstract: Erosion is a main failure of tubings and downhole tools in Changqing gas field. It is necessary to evaluate the erosion rate for the safety of tubing and strings. In this paper, the erosion of P110 steel, in the 0.2%wt guar gum fracturing fluid which contains sands, is investigated by weight loss method in the self-made jet experiment device. It is indicated that the erosion rate increases with the increment of slurry velocity exponentially. When the slurry velocity is in low velocity area, the electrochemical corrosion of dissolved oxygen dominates in erosion mechanism; when slurry velocity increases into middle velocity area, the weight loss is controlled by the synergism of corrosion-erosion; and when the slurry velocity increases into high velocity area, the weight loss rate is dominantly depended on erosion of particles. The results can provide guidelines for large-scale fracturing work of Changqing gas fields.

Abstract: Nowadays, most of the oilfields have been entered later development stage, it is difficult for reservoirs to depend on water flooding technology to improve recovery factor enormously. To satisfy deep flooding demand on heterogeneous reservoirs, the weak gel system is developed in the lab. Due to the mixture of organic chromium and HAPM, forming the organic weak gel system. HPAM concentration is from 1300mg/l to 1500mg/l and from 150mg/l to 210mg/l for cross-linking agent, the weak gel system formed stably with the high viscosity which is above 10000mp·s and moderate gelation time is from 45h to 130h.The best formula was selected with HPAM concentration 1500mg/l, and cross-linking agent concentration 210mg/l.The core displacement experiment shows the weak gel system has a well flooding effect on heterogeneous reservoirs, and its recovery rate increases 16.2%。