Surface Pressure Data for Well-Test Analysis at a Joint Venture Gas Project in Sichuan

DOI: 10.14800/IOGR.458

Abstract

Pressure Transient Analysis (PTA) of Bottom-Hole Pressure (BHP) data is a well-established method for estimating reservoir dynamic parameters and determining well behavior under different production stages. Unfortunately, permanent recording of bottom-hole data is not always operationally possible, particularly in the case of horizontal / high deviated wells and/or H₂S (sour gas) reservoirs, for safety and cost-effective reasons.  However, most wells are equipped with real time and digital gauges at the wellhead, which record well head pressure (WHP) and temperature (WHT) data continuously. What to do to maximize the value of the available information and to minimize the operational cost and execution risk?

This paper is to present the current experience at the Joint Venture gas project, utilizing the new converting technology, with which, WHP data can be converted to BHP data accurately during well shut-in.  With this success, the surface wellhead pressure WHP can be used for well-test analysis (i.e., PTA). There are several advantages in deriving the useful information from wellhead surface data: (a) the cost of recording wellhead data is much less than that of a downhole survey; (b) the risks associated with running tools in the wellbore are eliminated, particularly useful in horizontal / high deviated wells where tools cannot be run deep enough; (c) the work can be done any time where well shut-in is possible (both planned and unplanned downtime); and (d) this can reduce the significant production loss for any well intervention, particularly when spare gas supply capacity is low.

In brief, effective use of wellhead data is considered as an excellent technology application in China to minimize the traditional well-test intervention, which is with high cost and potential H₂S risk. Operational lessons learned and case studies on PTA will be shared.