Drilling Technology Research In Block B Of Tanhai Oilfield

With the ongoing exploitation of oil resources, the oil resources on land is becoming less and less, which makes the problem of oil shortage outstanding. The ocean covers more than 70% of the earth’s surface. Large amounts of oil and gas resources are buried in the subsea formation. So it’s very necessary to accelerate the pace of offshore oil and gases, especially the beach oilfields. The beach oilfields will be another energy base in future.This paper takes block B of one beach oilfield as the research object. Based on the block’s geology and engineering features, this paper studied the key drilling technology in this block, details as follow:Analyze the advantages and difficulties of twinhole-in-monobore technology; Analyze the enforceability of twinhole-in-monobore technology in block B according to the geology and engineering conditions; Sum up the construction procedure of surface drilling when the twinhole-in-monobore technology is used; Establish the collapse pressure and fracturing pressure model, considering the influences of inclination angle and azimuth angle and analyze the effects of the two angles on collapse pressure and fracturing pressure; Design the landing depth of surface casing and technical casing for a typical well in block B:Deduce the drag nnd torque calculating model, taking the huckling of dilll string into account; Analyze the drag and torque of drill string and optimize the drill assembly for Well B-6 in block B; design an individual PDC drill bit for gravel layer in Guantao group and Zhongshen erathem on the basis of rock-breaking mechanism, hybrid cutting theory, corona shape design theory, cutter design theory and hydraulic design theory.The results show that:The twinhole-in-monobore technology is an effective solution to the tight space of offshore platform; The safe mud density window is large and the window becomes larger when the inclination increases, which indicate that it’s suitable to drill directional well in block B; The well bore is most stable when the well drills along the direction of minimum horizontal principal stress; Block B is recommended to apply three-bud well structure with first bud sealing the soft formation above Pingyuan group and second bud sealing the easy lost and caving formation above Guantao group; The first spud is recommended to drill with φ406.4mm bit and the third spud is recommended to drill with φ215.9mm bit; To reduce the drag and torque of drill string and ensure the stability of drill string, the drill assembly in the third spud is recommended as 0215.9mm Bit+φ171.45mm PDM+φ151mm MWD+φ171.45 mm NMDC+φ139.7mm HWDP+φ139.7mm DP; In the drilling of second spud and third spud, PDC bit behaves much better than roller bit; The new designed φ215.9mm PDC bit and φ311.1mm bit achieve an increase of drilling rate in the gravel layer.The research methods and results provide a good reference for the drilling design and drilling construction in Block B and other similar beach oilfields.