Advanced Materials Research Vols. 616-618

Abstract: Reservoir pressure will decline generally along with production in the oil and gas development process. There are some problems such as borehole collapse or reduced diameter and lost circulation in drilling of initial production stage in unconsolidated sandstone. As the formation pressure declines the stress around borehole changes, and then collapse pressure and fracture pressure are affected. Especially in directional wells, variation of wellbore stability is more complex with different borehole deviation and azimuth. The calculation models of collapse and fracture pressure in depleted reservoirs were established, and relevant data in unconsolidated sand reservoir of an oilfield in Bohai Sea was used to calculate collapse pressure and fracture pressure of directional wells in the condition of pressure depletion before and after. The results showed that collapse and fracture pressure decreased as formation pressure depletion, and safe drilling fluid density window was wider when drilled to the direction of minimum horizontal principle stress. The calculation results can be reference to drilling design of adjustment wells in unconsolidated sandstones.

Abstract: Owing to the double actions by ternary liquid of ASP flooding and natural emulsifier in oil, the recovery liquid emulsified seriously as well as oil content in water rose after oil-water separation. Demulsification on recovery water in ASP flooding has been discussed via the modified terminal groups of hyperbranched tree macromolecules dendrimers polyamidoamine (PAMAM). Laboratory tests showed that PAE01 demulsifier had good demulsification efficiency. When demulsifier dosage was 120mg/L, sedimentation time was 90min, temperature was 45°C, oil content in water dropped from initial 5000mg/L to 197mg/L after demulsification, the deoiling rate was 96.1%. When initial oil content was 1500mg/L, oil content in water dropped to 215mg/L, the deoiling rate was 85.7%.

Abstract: Based on the Turner’s liquid-loading model for gas wells, combined with Liquid Membrane Breaking Theory and Law of energy Conservation, a new liquid-loading model for mist flow in wave shaped crushing mode for gas-liquid wells was put forward, and a new equation for critical liquid-loading gas flow rate estimation was derived. The results show that the lowest conditions for liquid loading is that most of liquid drops can continuously move upward in gas flow, and when radii of liquid drops are smaller than 1600μm, liquid drops in the wellbore are basically in spherical shape. The critical liquid-carrying gas flow rate, in gas wells, calculated with this new model, is more reasonable and accurate.

Abstract: Considering the reservoir seepage, borehole wall inflow, fracture and perforation flow’s process and mutual influence, an unsteady state computation model of fractured horizontal well coupling with reservoir was established based on the source function and superposition principle. Calculation results showed that compared to the production only from the hydraulic fractures, the difference of that both from fractures and perforations was great early and decreased slowly later. Take the perforation production for example, because of mutual interference and well bore flow friction, different location perforations with different output and the central-perforation production was lower than that of the outer-position.

Abstract: Results of polymer flooding oil production forecast will directly affect annual planning and long-term planning deployment in oil field development, so the choice of forecasting model is particularly important. On the basis of briefly introducing the optimal combination forecast model, the optimal combination forecast model is established based on the Weibull prediction, HCZ prediction and generalized Weng forecasting methods. The weight coefficient of the optimal combination forecast model is determined by the criterion of the minimum square sum of the forecasting error. It realizes that the production prediction model is optimal combination. The precision of the optimal combination forecast model is compared and analyzed with the other prediction models, such as Weibull prediction model, HCZ prediction model and generalized Weng model by using the real data. It proves that the optimal combination forecast model of polymer flooding is effective and practical.

Abstract: Fractured horizontal well is the important means for the development of tight gas reservoirs. Based on the geologic characteristics of the tight gas reservoir, a pressure transient model for fractured horizontal wells is established by the Green functions and Newman product principle. The model considers the seepage resistances and the inferences from fractures each other. Practical application presents the pressure changes and flow rate distribution of fractures at non-steady state and quasi-steady state, and the suggestions for field operation are given as well.

Abstract: The earth filtering is inevitably in seismic wave propagation and the parameters to represent earth filter intensity is the absorption coefficient and the Q value. Using zero-offset vsp's down-going direct wave to estimated Q value is considered the most reliable way to extract stratigraphic quality factor Q value. We used Ken 71 well zero-offset VSP down-going direct wave with the centroid frequency shift method to estimate layer Q value. First, by processing the zero-offset VSP data, we separated down-going-direct wave and up-going wave. Then, we analysis and calculated the layer-velocity and layer Q value using down-going wave. At last, we made the bridge comparison chart by the up-going-wave processed. The bridge comparison chart compared with the layer-velocity and layer-Q value, results show that the corresponding relations are very good.

Abstract: Different types of micro-pore structure and variation characteristics after long-term washing have a greater impact on micro-remaining-oil migration direction, distribution and content. This article applied Confocal Laser Scanning Technology to study reservoir fluid property and remaining oil micro distribution after strong alkali ASP flooding. Comparing the Laser Confocal analysis pictures of natural core after water drive and ASP flooding, coming to the conclusions that strong alkali ASP flooding sweep out larger amounts of heavy oil than water drive. Counting the ratio of different types micro-remaining-oil, and analysing on the displacement effects and mechanism of different types remaining oil after strong alkali ASP flooding.

Abstract: Influenced by special geologic condition and stimulation, the production performance of tight fractured gas well is obviously different from that of conventional gas well. During deliverability testing, the hydraulic fractured gas well can never reach steady state with limited test time. It is difficult to calculate reserve and drainage area accurately at early development stage. Take eastern Sulige gas field for example, by correctly recognizing the percolation characteristics and production performance of hydraulically-fractured tight gas wells, and combined with core analysis, 116 hydraulically fractured tight gas wells in eastern Sulige gas field have been analyzed. A prediction chart of recoverable reserve for estern Sulige gas field is established. With this chart, the ultimately recoverable reserves, drainage sizes, drainage lengths and drainage widths of 116 hydraulically-fractured tight gas wells in eastern Sulige gas field are predicted based on early stage of production data, and finally a reasonable well spacing for this field is suggested. Only utilizing routine production data without employing additional resources, this method is a good predictive guide to launch a development plan of tight gas field.

Abstract: China is facing a severe situation of energy resources. High oil dependency is seriously threatening our economy’s fast and stable development. The US has successfully achieved the commercial development of shale gas, which has decreased its oil dependency, and also contributed to its natural gas geology and petroleum engineering technology development. Both Chinese and U.S. geological experts predict that China has similar quantities of shale gas reserves as founded in the United States. This paper aims to clarify that producing shale gas resources has economic significance of energy security and environment protection, and scientific significance of promoting the further development of natural gas geology and petroleum engineering subjects.