Branch Well Connected Well Section Sidewall Mechanical Stability

Currently, Multilateral well technology has been widely used in oil-field gradually. Great potential in increasing the possibility to drill to the targets and improving production, lateral well technology has aroused deep interest of the oil companies and oil-field service companies. With the improvement of lateral well technology, branch wells will be an important part of the development of the smart wells. The technology, however, is also facing some new challenges, and the most important one is how to resolve the problem of borehole stability of multilateral junctions, for which will cause the borehole wall sloughing of junctions and wellbore abandoning. In the North Sea oil fields, there are several lateral wells encountering wellbore instability problem in the operating process. For the successful operations of drilling and completion of the branch wells. it is necessary to maintain borehole stability in construction process. Based on elastic theory and rock mechanics, the mechanical stability of wellbore of multilateral junctions is analyzed and researched.Firstly, the well borehole stability analysis model of lateral well is established, and the stress distribution around a vertical well and deviated wells is detail analyzed and deduced, based on which a geometric model of multilateral junctions is established and its force conditions are discussed. Finally a formula for calculating the fracture pressure and collapse pressure of multilateral junctions is obtained.Secondly, giving the method for determining the rock mechanical parameters, crustal stress and pore pressure. The methods for determining stress are described in detail, such as hydraulic fracturing method, acoustic emission method and the log data method, predicted before drilling, drilling, testing and drilling, etc.Finally, in order to analyze the law of stress distribution and mechanical stability, the three-dimensional geometry models and finite element models are established. Making use of the rock and fluid parameters of a lateral well in eastern oil field wells and according to the change of the deviation angle on the export of branch. an analogue computation is performed on the multilateral junctions, so that the stress distribution cloud, displacement distribution cloud and wall fracture situation on various deviation angle are obtained.In practice, according to the specific situation of the oil field, the combination of theory and practice can prevent and timely treat the accidents of borehole instability. Borehole instability of multilateral junctions is a complicate problem to which further research is needed. Finite element numerical simulation can provide accurate drilling engineering reference for the practical application of engineering to meet the on-site drilling fluid density to ensure the safety of the drilling process, orderly conduct.