Research On Underbalanced Drilling Technology Of Structure Buried Hill 1,2 Of Jidong Nanpu

The deep zone and high temperature buried hill of Nanpu hydrocarbon reservoir is characterized of deep bury(vertical depth from 3500 to 5700m),low formation pressure(from 0.96 to 1.06),high reservoir temperature(from 160 to 210?),high gas-oil ratio(from 1309 to 30000 m3/t),and uneven distribution of cracks.According to preliminary exploration,although the oil and gas were found during conventional drilling,but did not found industrial oil and gas flow except for the LPN1 well in the area.The high reservoir damage induced by drilling fluid affects the discovery of oil and gas and even the production of reservoir,which restricted the exploration of the buried hill reservoir.The fractures of buried hill reservoir were relatively developed,which may lead to leakage(average:1000m3)and overflow(average disposal period:10 days),and other underground complex accidents.Meanwhile,severe leak(more than 2,000 m3 in the No.2 buried hill well)during well completion,high risk of well-controlled and long drilling cycle(average:220 days)all cause more underground complex accidents and high drilling cost,these factors limit the exploration and development in the area.Based on the exploration and development demand of the deep zone and high temperature buried hill of Nanpu reservoir,we analyzed the data on geological engineering and found that the leakage and overflow is serious and bore hole stabilization of carbonate formation.The application of underbalanced drilling techniques in the area is appropriate and necessary.Considered the density compression of drilling fluid and temperature characteristics,we established an instantaneous model of gas-liquid two-phase flow and analyzed the key technology of underbalanced drilling's security control technology in an example.The theory of underbalanced drilling safe density window and the field data was analyzed,a quantitative grading method of underbalanced drilling was proposed which under high gas oil ratio,which provided a basis to determine the rational bottom-hole underbalance pressure in the deep zone and high temperature in underbalanced drilling.The safety and risk assessment techniques and parameters' analog control system in underbalanced drilling operation were formed by developing research of MWD and reservoir evaluation technology.According to the research of field application of underbalanced drilling technology in 1,2 wells,including considered the whole planning,field experiment,application effect and underlying problems,HTHP deep underbalanced drilling technology were formed.It has been achieved successfully preferable results in the exploration and development of the buried hill in Nanpu,effectively solved the problem of serious leakage and overflow,shortened drilling cycle and decreased the drilling cost and obtained better economic effects as well as good social effect.