A New Method for Predicting the Depth of Karstic-fault Reservoir with Well Temperature Log

Abstract

In the exploitation of oil and gas resources, when the development area is Karstic-fault carbonate reservoir, large borehole collapse is often encountered in the process of drilling, so conventional logs cannot be obtained, and the borehole even cannot be drilled directly into the reservoir. In this case, the reservoir is connected with the well through fracture and cave, and there is oil and gas production in the well, but it is difficult to determine the reservoir depth through log evaluation, then it's difficult for subsequent long-term oil and gas development. Because it is not affected by borehole factors, the well log of temperature becomes the only available logging log. In order to explore the method of predicting reservoir depth by using well temperature log. The fluid flow field and temperature field in the well were coupled with the formation temperature field by using the numerical simulation method centering on computational fluid mechanics. In the case that the well is directly connected to the cave reservoir, the effects of fluid flow rate, production time and shut-in time on the well temperature log are researched by simulating the temperature changes in the well in both transient and steady-state modes. When the cave reservoir is at the bottom of the well, the flow temperature measured at the bottom of the well is the same as the static temperature. When the cave reservoir and the well are connected by cave, the source depth of the fluid can be determined by the temperature log.