Borehole Stability Analysis And Sand Production Prediction Of Buried Hill In Bohai Sea

The Bohai buried hill trap is important for the oil and gas reservoirs of Bohai,which is of great significance for China to increase its reserves and production.However,the geological conditions of the buried hill formation are complex,and hard and brittle shale formations have cracks and micro-fractures,with instability and short collapse period.There will be great safety hazards during drilling and completion.In this paper,based on the characteristics of the buried hill formation in the BZ19-6 oilfield,the stability analysis of the buried well and the prediction of sand production are carried out to provide a certain reference value for the safe and efficient drilling operations.This paper focuses on the characteristics of geological drilling in the buried hills,taking BZ19-6 and 34-4 block as an example to carry out macro and micro analysis of the composition of hard and brittle mud shale,and study the causes of borehole instability and complex drilling conditions.The geostress orientation is determined by logging data and experiments.The pressure profile of 11 wells are drawn with Drillworks and singletriaxial experiments,so a rock mechanics model was established more accurately.The risk map of collapse and fracture pressure was drawn,so that the drilling direction of the horizontal section was optimized.The safety density window was given.The result provides a reference for on-site construction operations.Comparing bubbling strength experiment,it is found hydration has a certain effect on the wellbore stability.It shows that compared with the unimmersed drilling fluid,the strength and elastic modulus of the immersed drilling fluid decrease to a certain extent,and Poisson's ratio increases greatly.At the same time,the critical pressure difference method and sonic time difference method are used to analyze the possibility of sand production in the reservoir,the effect of reservoir pressure failure on the critical pressure difference in sand production is calculated,and the occurrence of buried hill reservoir prediction The possibility of sand is small.Since there is no mature research system for sand production in buried hill formations,the traditional sand production prediction method is still used,which has limitations.