Advanced Materials Research Vols. 734-737

Abstract: Because of the inclination of borehole, there is a significant difference about the borehole stability between deflecting and vertical well. Borehole stability has a relationship with not only trajectory of well, including deviation angle and azimuth, but also azimuth of earth stress. This paper will start from stress field of wall of borehole to study borehole stability in inclined well. And with suitable destruction model of wall of borehole, the reasonable dynamic model and determine the safe mud density of deflecting well can be obtained exactly. The new model is used so as to calculate and determine the safe range of mud density in penetration and round-trip operations.

Abstract: This paper presents a simple two-phase flow model for liquid-cut gas wells, which considers phase slippage and can be applied to various flow patterns. The model is developed from 312 measured pressure losses of gas wells in China, covering a wide range of flow patterns: annular flow, churn flow, and slug flow. Unlike most available methods, this new model introduces a derivation factor, ψ, to modify the void fraction, which not only considers the phase slippage but also unifies the slip model with the homogenous model. Parameter, ψ, is obtained from test data using the regression analyses method. It is a function of gas velocity number, liquid velocity number and liquid viscosity number. Frictional factor is estimated using the simple homogeneous modeling approach. The evaluation results using 145 published data indicate that the new model performed better than the other models.

Abstract: The fluid flowing resistance increase and the water absorbing capacity reduce due to the threshold pressure gradient and media deformation of the low permeability reservoirs in the course of development. The oil production of vertical wells may decrease fastly and the controlled reservers are hard to recover. The development effects are not satisfied. Through great fracturing measurements create many fractures, and fractures extended along the direction of well line, the long fracture channels were formed like horizontal well segments. This kind of long fracture was called as horizontal segment of imitation horizontal well. It can broad drainage radius in production well and increase controlled reserves and daily oil production of single well. In this paper, the influence factors of the low permeablity reservoirs development by imitation horizontal wells were analysised. Through well pattern, well distance, line distance, injector and producer parameters and fracturing parameters of imitation horizontal well optimization, drainage radius in lower permeability reservoirs can be reached to 200 meters, the daily production in single well can increase two times of that before, and the production result was improved greatly in lower permeability reservoirs development.

Abstract: The separate layer water injection rate determines the result of water injection. In the past, in order to inject a proper amount of water into different intervals, most of the time people would rely on their experiences. By employing this method, the amount of work was enormous and the result was not necessarily accurate. In this paper, five factors that would affect the water injection rate are taken into consideration, such as, thickness of the main well, the connected thickness, permeability, number of connected wells and oil saturation. A method of determining the proper water injection rate of single wells based on analytic hierarchy process is proposed. This method has been proven to be simple and accurate, the test result of a mathematical model also shows it fits the requirements of the oil field exploitation with current water cut and it is of great value to practical applications.

Abstract: In this paper, combining previous research on methods of determining water injection rate, dividing coefficient is introduced into this process. Influential factors of water injection rate are also taken into consideration. Based on those theories mentioned above, an analysis on determining dividing coefficient is made by applying BP neural network. Data from one particular year of exploitation was chosen to build up a neural network model between the dividing coefficient and other factors to determine the dividing coefficient, and then single well water injection rate was determined.

Abstract: In the log interpretation, the CBM content evaluation methods include: regression, LAN’s equation, KIM method, neural network, and so on. This paper investigates the suitability of these methods for a CBM reservoir in Southern Qinshui Basin, Shanxi Province of China, and finds out the most reasonable interpretation model of CBM content in this area. The results show that the composite parameter(COMP) method and the LAN’s equation method are more suitable for evaluating the CBM content in this study area, while the other methods are not.

Abstract: As an attempt to contribute to the understanding of the corrosion processes of anti-sulfur steel in CO₂ and H₂S containing environment with different species, the corrosion behavior of SM 80SS tubing steel immersed in CO₂ and H₂S containing solution was analyzed in this work. To determine the corrosion behavior of SM80SS steel, the linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques were used, as well as weight loss test and surface analysis. The results showed that the presence of Cl^- quickened the anodic dissolution processes and rapidly increased the corrosion rate of SM 80SS steel, and that the addition of Ca²⁺ and Mg²⁺ reduced corrosion rate. The corrosion processes of SM 80SS steel were controlled by the electrochemical reaction in the initial period and then converted to be controlled by electrochemical and activation reaction with increasing Cl^-. Keywords: SM 80SS tubing steel; CO₂/H₂S corrosion; EIS; Chloride; Ca²⁺ + Mg²⁺

Abstract: The selection of profile control layers is based on the decision made by single factor at present. Fuzzy cluster analysis based on transitive closure is introduced to establish an evaluation model of profile control layers' selection. Firstly, combining the static geological data and dynamic development data, the evaluation indexes which affect the selection of profile control layers are screened to form the evaluation index system; secondly, according to fuzzy cluster analysis theory, the evaluation index matrix related to profile control layers' selection is dynamically clustered, and the profile control layers are selected on the basis of each category's characteristics of geological and development; finally, the results of profile control layers' selection are examined by the comparison of water injection profile. In addition, the evaluation model is put into practice in a testing well group, and the application shows that the profile control layers selected by the model is reasonable and reliable.

Abstract: Zhanazhol oilfield is a large-scale complicated carbonated oil and gas field , Гnorth is the main oil and gas reservoirs of the oil field, The gas cap index is 0.38, the gas cap on a high condensate content. Reservoir development for nearly 25 years, exploitation in the past only to oil ring. Due to insufficient water injection in early age, the oil ring pressure dropped substantially, and the formation pressure to maintain the level of only 58%. For oil and gas reservoirs with a condensate gas cap, gas cap and oil ring at the same pressure system, with the decline in the pressure of the oil ring, the gas cap continue to spread to the oil region, while there are a large number of condensate oil anti-condensate from the gas cap, which loss into the formation. In this paper, the authors consider the characteristics of the oil and gas reservoirs and research the technique policy of collaborative development, These are all in order to solve technical problems, which is keep the pressure balance between the gas cap and oil ring during collaborative development. Not only provide technical to support the rational and efficient development of the Г North oil and gas reservoirs, but also provide a stable source for natural gas pipeline from Kazakhstan to China.

Abstract: Guided by the theory of petroleum system, we analyzed hydrocarbon accumulation elements and conditions of the Shahejie Formation in Tangzhuang area and concluded the hydrocarbon accumulation model based on the geological and geophysical data. Hydrocarbon comes from the source rock of Es₃ in Linyi sub-sag located to the southeast of Tangzhuang area. Reservoir mainly is clastic, followed by carbonate. There are 4 source-reservoir-cap assemblages in the Shahejie Formation. The Es₃ source rock of different tectonic units in Linnan sub-sag has experienced different hydrocarbon generation stages. The central region experienced two hydrocarbon generation stages while the edge only experienced one stage. The hydrocarbon generated by the source rock of Es₃ in Linnan sub-sag mainly migrated to Tangzhuang area along fault and sand body. The structural trap is the dominant type followed by structure-lithologic trap and lithologic trap. Based on the analysis of hydrocarbon accumulation condition, we concluded the lower generating and upper reserving model of the study area. The findings will play an important role in guiding Tangzhuang oil and gas exploration.