Research On Key Technology Of Wellbore Integrity For Drilling Engineering In Xushen Gas Field

Xushen Gas Field is an acid gas reservoir with high pressure,high temperature and high CO₂ content.The reservoir is mainly volcanic rock,the fracture is relatively developed,the rock is of high hardness,high abrasive property and high drillability.There are drilling accidents and other problems such as circulation loss,low drilling efficiency,increased drilling risk time.In the process of drilling and completion,once the blowout occurs,it will cause huge social and economic losses.So the wellbore integrity of drilling engineering should be highly required.In view of the above problems,the deep research on improving the wellbore integrity of drilling engineering in Xushen Gas Field is developed deeply in this paper.The main work and research results are as follows:The comprehensive prediction and identification technology of fractures in Xushen Gas Field is emphasized.The main parameters of fractures in Songliao Basin can be obtained by compiling Ansys post-treatment fracture calculation module based on genetic fracture prediction technology.The data obtained from the prediction model is highly reliable and can predict the development effectively of fractures in Xushen Gas Field.Some medium or large size fractures of directions can be predicted effectively by using automatic ant body tracking technology.Fracture identification technology based on artificial fish swarm algorithm can identify and predict fractures effectively by using well logging data after drilling.The comprehensive application of the three methods to predict the distribution characteristics of fractures in Xushen Gas Field can effectively predict the development of fractures in drilling areas and guarantee the integrity of the wellbore during drilling.The research on the method of preventing and sealing leakage in Xushen Gas Field based on case-based reasoning is emphasized.Firstly,the fracture stability mechanism and leakage mechanism of igneous rock stratum are analyzed.The leakage prevention and sealing technology based on case-based reasoning is carried out to be as the relevant feature vectors.The evaluation of the plugging effect in the ignite chamber of Xushen Gas Field is carried out from the aspects of plugging performance,bearing capacity and plugging effect.A set of plugging agent formula that can effectively seal the 1?3mm fractures has been formed,and the bearing capacity is more than5.0 MPa.The case-base of well leakage in Xushen Gas Field is established which based on a large number of well leakage cases in Xushen Gas Field in the past,and form a research method of leakage prevention and sealing in Xushen Gas Field based on case reasoning.This method can comprehensively analyze the complex well leakage in the process of drilling based on the previous well leakage cases,and formulate the new leakage sealing measures according to the previous methods.At the same time,it can also predict the occurrence of well leakage according to the actual working condition of the new drilling and take the leakage prevention in advance.The high-efficiency water-based drilling fluid system of anti-high temperature in Xushen Gas Field was studied.Laboratory tests were carried out to evaluate the inhibitors,viscosifiers,thinners,fluid loss reducers and lubricants of drilling fluids.A set of high temperature resistant and efficient water-based drilling fluid system in Sushen Gas Field was formed.In view of the performance characteristics of the drilling fluid system,the performance evaluation method of drilling fluid based on the reliability technology of performance degradation was studied.Firstly,the failure analysis of drilling fluid is carried out to study the performance degradation data and establish the drilling fluid degradation failure model.The reliability evaluation was carried out according to the main performance of drilling fluid,and the performance evaluation of drilling fluid was carried out through the performance degradation data of filter vector,dynamic plastic ratio,plastic viscosity,mud cake adhesion coefficient and extreme pressure lubrication coefficient.According to the evaluation,the filter vector with performance parameters has the highest failure probability and the shortest failure time at 90h.Therefore,according to the performance evaluation method based on performance degradation drilling fluid,the filtration vector performance of drilling fluid should be strengthened.By optimizing more effective drugs,the filtration stability of drilling fluid can be improved,so as to improve the failure time of drilling fluid and extend the service life of drilling fluid.The performance evaluation technology of CO₂ corrosion resistant casing in Xushen Gas Field was studied.The mechanical properties of 13cr-95,hp13cr-110 and 11cr-110 were analyzed and evaluated.The analysis of the anti-CO₂ corrosion performance is mainly carried out.Through the CO₂ corrosion rate test,the corrosion rate fitting was carried out,and the anti-CO₂ corrosion index was introduced to predict the anti-CO₂ corrosion rate of the casing accurately.