Bohai L oilfield has undergone multiple adjustments since it was exploited, such as well pattern internal infilling, changing well patterns, and reversing lines. The scattered distribution of remaining oil on the flat and extremely complicated vertical flooding law resulted in difficulty for tapping the remaining oil. Based on the data of core, well logging, seismic, production dynamic and other results, the thick reservoir can be comprehensively characterized, so as to guide the remaining oil fine characterization and potential development. The results show that the plane contact styles of single sand body is mainly in butt type, and the vertical overlap mainly in cut type. The remaining oil of the southern vertical accretion type leaf body is mainly concentrated near the vicinity of the fault, the buried hill area and the sand?body deposition margin, which can be tapped using directional wells. The remaining oil of the central prophase frond is mainly concentrated in the top of the thick sand body and the lower part of the thin interbe, which can be tapped using horizontal wells.

Serious well collapse in the 2h well horizontal section of a CFD oilfield took place during drilling in carbonaceous mudstone before landing. In order to satisfy the requirements of drilling the rest wells, the analysis of drilling collapse and the research on anticollapse countermeasures were carried out. By investigating the correlation between drilling fluid performance and wellbore collapse,bedding structure and clay minerals, the low drilling mud density, and the poor performance of plugging and anti?swelling were determined to the main factors leading to the well collapse. From the point of view of mechanical countermeasures, the relationship curve between well deviation and collapse pressure were established based on the strength anisotropy model, for the future selection of mud density. In view of chemical countermeasures, 1% inhibitor along with 5% calcium carbonate and 1% nano?materials as plugging agents were added in the drilling fluid. The results show that the cuttings roller recovery using optimized drilling fluid could reach to 91.39%, the dynamic HTHP filtrate loss performance be decreased by 22.41%. The point load strength of the optimized drilling fluid is only 13.60%, which is superior to the original one of 32.45%.The research results can provide reference for solving the problem of lack of physical data and urgent need of anti?sloughing measures.