欠平衡钻井环空多相流井底压力计算模型

随着欠平衡钻井技术的发展,对井底负压值精确控制的要求越来越高,目前已经开发了随钻井底压力测量仪器。对井底压力的大小实测发现,原有的气液两相流井底负压控制计算模型的计算误差较大,达到13%。为此,在H.V.Nickens所建立的钻井过程气侵时的两相流模型基础上,建立了直井环空多相流井底压力流动型态新的计算模型。该模型充分考虑了岩屑固相和多相加速度压降的影响,精度较高,利用深层欠平衡钻井实测数据,计算表明误差小于3%,为欠平衡设计计算与精确控制井底负压值提供了理论依据。

New model for calculating bottom hole pressure of multiphase flow in annulus of underbalanced straight well

Following the development of underbalanced drilling technologies,it is necessary to accurately control the underbalanced bottom hole pressure.The bottom hole pressure (BHP) measuring instrument while drilling can be used to measure the BHP in real time.The measured results showed that the calculation error of bottom hole pressure of gas-liquid phase flow calculated by the original method is up to 13 percent.On the basis of gas-liquid phase flow model for gas cut while drilling established by H.V. Nickens,a new flow type model for calculating BHP of annulus multi phase flow in straight well was presented.The influences of cuttings and gas-liquid acceleration pressure drop were considered in this model.The model has high accuracy of calculation.The underbalanced pressure calculated from this model proved by actual measured data in deep formation indicated that its error is less than 3 percent.The model can provide theoretical base for the accurate control of underbalanced bottom hole pressure and underbalanced design calculation.