Research On Evaluation Method Of Adaptability Of Underbalanced Drilling Application

The underbalanced drilling technology has been acquired rapid development no matter in the domestic or overseas at present, the progress of technology and special equipment itself could adapt to requirement of underbalanced drilling which for all kinds of well-type and different ways of circulating fluid. The pre-evaluation of underbalanced drilling technology is not sufficient and systematic so that the application effect is not ideal. It seriously influences the scope and scale of promotion and application for the technology. So it is necessary to carry out the research for adaptability evaluation methods of underbalanced drilling. The adaptability evaluation content for underbalanced drilling applying that mainly includes technical feasibility and economic available evaluation. The technical feasibility mainly evaluates geological adaptability of the technology. It is from three aspects to carry out the appraisal analysis which are formation pore pressure, formation stability and formation fluid output. Whether or not it could choose the proper ways of underbalanced drilling and implement the safe drilling based on the geological conditions judgment. Then it could exactly predict the adaptability of underbalanced drilling to the geological conditions. It also structures the speed-up calculation model and method of underbalanced drilling and completes quantitive prediction and evaluation for the increasing penetration rate effect of underbalanced drilling. The increasing productivity calculation model can quantitive predict and evaluate the late productivity improvement. It establishes the theoretical foundation for accurately evaluate the effect of underbalanced drilling. The economic available evaluation applies underbalanced drilling to increase the penetration rate calculation model and the productivity calculation model with considering all kinds of costs of conventional drilling and underbalanced drilling. Thus it can calculate the composite economic results of comparison within conventional drilling and underbalanced drilling.Through the evaluation of technical feasibility and economic available, the paper will know whether the pre-drilling applies in underbalanced drilling, how much the economic benefits from underbalanced drilling when making sufficient evaluation and whether or how to carry on underbalanced drilling making the more scientific decision.