Using Pressure Gradient Survey as a Cost-Effective Diagnostic and Decision-Making Tool

Abstract

Locating the water entries in an oil producer is critical for the success of remedial work, such as acid stimulation and water shut off, to prolong the life of the well and enhance production. Different logging tools are successfully used to obtain this information such as PLT. Practicality of using these logging tools can be limited. A good example of these limitations is a well that cannot flow or sustain flow to surface (dead well). Therefore, in addition to the historical data, previous PLTs, water drive mechanisms for such wells, along with the well performance history, the pressure gradient survey approach is used to come up with best estimate of static OWC in vertical or slightly deviated wellbores. This paper will answer the questions of when, and why conduct a pressure gradient survey and the optimum running procedure by discussing the utilization of the pressure gradient survey as a diagnostic and decision-making tool in a few case histories from the Ghawar filed in Saudi Arabia will be discussed. Introduction Locating oil water contact, OWC, in the wellbore is essential before any well intervention or remedial work such as acid stimulation and water shut-off. The current best tool for such information is the production logging tool, (PLT), which gives the flexibility of seeing both the dynamic, and static OWC, however running the PLT even though it seems as the only tool, is not always a cost-effective way. Therefore, in addition to the historical data, previous PLTs, water drive mechanisms for these wells, and the well performance history. The pressure gradient survey approach is used to come up with the best estimate of the static OWC in vertical or slightly deviated wellbores.