Acquisition of Downhole Pressures without Downhole Gauges in the Gulf of Thailand via the Self-Powered Intelligent Data Retriever

Abstract

Bottomhole pressure is one of the most important sources of data used to determine reservoir characteristics. By analyzing the manner in which bottomhole pressures change with time and flow rate, properties can be derived such as permeability, skin, boundaries, and reservoir pressure, which can enable the evaluation of hydrocarbon reserves and make economically feasible decisions. Downhole pressure data in production wells are most commonly acquired by running downhole pressure gauges on slickline into the wellbore. However, in offshore wells in remote locations, there can be major deterrents to capturing bottomhole pressures using slickline. Examples of these limitations include equipment and manpower availability, crane functionality, and offshore accommodations. Furthermore, there can be physical limitations to data acquisition from the presence of sour gas, high bottomhole temperatures, high wellbore deviation, or mechanical obstructions that can prevent the use of downhole gauges in the well. This paper presents an innovative method for acquiring the needed bottomhole pressures in production wells when traditionally used methods may present challenges. An operator in the Gulf of Thailand wanted to obtain downhole pressures on their production wells but did not wish to run slickline and downhole gauges because of the concerns specified above. A new self-powered intelligent data-retriever system was suggested to the operator as it offered a method that could derive accurate bottomhole pressures without running downhole gauges. The new system consists of a high accuracy, high resolution pressure gauge and a companion bottomhole pressure conversion algorithm. The pressure gauge is installed on the wellhead and captures high-frequency surface-pressure data. The conversion algorithm uses the surface pressure data, along with wellbore information, and fluid properties to calculate downhole pressures. The results of a series of tests with the self-powered intelligent data-retriever system demonstrated that the system can provide accurate bottomhole pressure results in production wells. These facts will be verified by the test results as well as the case history, both of which will be presented in this paper. This technology was designed to reduce the cost of capturing downhole pressure data, lessen many of the logistical concerns that could occur when using traditional systems, eliminate the risks of a downhole gauge getting stuck in the wellbore, and acquire necessary data when downhole environments are corrosive.