The Calculation Method of Bottomhole Pressure during Shut-in Period in High Temperature and High Pressure Gas Well

In the conventional method of bottomhole pressure prediction it is assumed that the wellhead pressure is affected by the wellbore storage at the beginning of pressure buildup and by the afterflow in the late stage because of the temperature drop.And it is also assumed that there is no fluid flow in the wellbore after shut-in.However,according to testing results of some high pressure and high temperature wells in Kela-2 Gas Field,there was a pressure drop in the wellhead pressure build-up curve which is different from the conventional pressure build-up curve.The changing characteristics of wellbore temperature,the wellbore afterflow and the fluid parameters during the pressure build-up test then were analyzed.It is believed that the wellhead pressure or bottomhole pressure would be affected by both wellbore storage and wellbore temperature simultaneously.And there was afterflow in the wellbore during the whole test.So,the bottomhole pressure needs to be calculated by the flowing pressure equation.Based on the wellbore pressure build-up theory,the bottomhole pressure calculating model is established considering the effect of wellbore afterflow,the wellbore temperature changing and the fluid parameters changing.Taking one gas well for example,the pressure buildup curve calculated by this model is normal,and it can be applied for interpretation in the deliverability test.