| With the development of petroleum industry, the directed drilling technique is widely used during exploration and exploitation. And the wellbore stability problem becomes more and more predominant, which seriously influences the process of exploration and exploitation. Unlike the vertical well, wellbore stability of the directional well varies from changes of deviation angle and azimuth. Therefore, the research on wellbore stability of the directional well will encounter enormous opportunity and challenge. Actual exploration data shows that the Panyu10-2/4/5/8oilfield is consisted of shale and argillaceous sandstone and the porosity is large, good permeability, wellbore wall sloughing. Zhuhai group leaks seriously during electric measurement process; Hanjiang group and Pearl River group resists, cards frequently while drilling, which seriously restricts regional exploration and development process. It is contradictory to efficient development of Panyu10-2/4/5/8oilfield. Therefore, this domain is required to study fault distribution and analysis the mechanical properties of rock and earth stress based on fault distribution, and then research the fault leakage mechanism and analysis stability of the directional well borehole, in order to improve the exploration development rapid. We hope that "safe, efficient, high quality, economic" development will be realized and a strong technical support will be proved.First of all, in this paper the geological, logging and drilling data are used to establish pore pressure profile of the studied blocks that have been drilling; through the pore pressure results, combined with the geological conditions, find out formation pressure vertical distribution law of the researched block; according to the study of structural features and formation connectivity characteristics, research the lateral distribution law of each layer pore pressure, and form the contour map of formation pore pressure distribution. Secondly, based on the analysis to the block tectonic movement process, initially determine relative ground stress; through hydraulic fracturing test, define ground stress of test point or coring bit; considering physical properties of different rocks, mechanical properties and abnormal pore pressure differences, set up stratified stress computation model, identify tectonic stress coefficient and combined with logging data interpretation to longitudinal reservoir stress, establish longitudinal stress profile; on the basis of the characteristics of regional stress zoning, combined with ground stress direction of the studied adjacent block, apply borehole breakout method to determine the direction. Again, according to the core test results and the corresponding well logging data, build and confirm the calculation model to predict rock mechanics parameters. The experimental data analysis of the borehole stability is proved. Then, analysis borehole stress distribution, combined with the rock failure criterion, establish the calculation models of the formation fracture pressure and collapse pressure, study the risk on borehole instability in the different inclination and azimuth. Finally, built sandstone creep constitutive equation, through indoor experiment, determine the creep parameter values of the sandstone reservoir, and in accordance with the35%wellbore shrinkage degree, safety drilling cycle is well estimated in the horizontal section and we can draw the map of safety drilling cycle; according to the calculation, it is not apparent to see the Panyu10-2/4/5/8oilfield’s creep problem which is caused by viscosity of the reservoir sandstone. In addition, according to the current ocean drilling skill and speed, the drilling safety problem caused by creeping will not occur.In this paper, the theoretical basis is provided for the studied block directional well design, but also for technical support to the directional well drilling technology in the Panyu10-2/4/5/8oil field. It has played a very positive role in promoting wellbore stability. |
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