Integrating Fractional Flow Into Reservoir Surveillance Improves GOM Production
Authors: Feder Judy 
Published: September 2019

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 192843, “A Success Story of Production Improvement in a Deepwater GOM Field Based on Integration of Surveillance Techniques,” by Fabio Gonzalez, SPE, Doris Gonzalez, Steve Carmichael, SPE, Carlos Stewart, SPE, Marney Pietrobon, and Francisco Garzon, SPE, BP America, prepared for the 2018 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 12–15 November. The paper has not been peer reviewed.

Integration of well and reservoir surveillance techniques—production measurements, reservoir fluid characterization, pressure transient analysis, production logging, relative permeability, and fractional flow—are critical to understanding well and reservoir performance for effective well and field management, particularly in high-cost intervention environments. The complete paper presents a case study in the deepwater Gulf of Mexico (GOM) in which pressure transient analysis (PTA), fractional flow (FF), and production logging tools (PLT) were integrated to identify correctly the cause of, and execute an effective remedy for, a•well’s productivity deterioration.

Background

The level of integration achieved in this study is not common practice because most commercial software products do not consider multiphase interpretations in analytical PTA. These limitations leave out the actual effect of relative permeability in the estimated transmissibility values. In this case, integrating fractional flow analysis with a multilayer PTA curve and running a production-logging tool made it possible to separate relative-permeability effects from plugging effects. A coiled-tubing (CT) mud acid-stimulation treatment then enabled recovery of approximately 65% of the well’s lost transmissibility, decreased formation skin from 16 to 9, and instantaneously restored 7,000 STB/D of production. This analysis approach has been recommended to determine the potential production-optimization benefits of future intervention candidates. The complete paper discusses the geology and reservoir characterization of the well, its initial performance and subsequent deterioration, the surveillance tools used to evaluate the well’s performance and determine the intervention method and steps, a comparison between basic diagnostic PTA and multilayer PTA, the building of the multilayer model, the execution of the stimulation treatment, and the results and conclusions of the program.

Field Case

A subsea deepwater GOM well began production in 2009 with an initial rate of 35,000 STB/D with no water production and a gas/oil ratio (GOR) of 1100 scf/STB. The well was equipped with a downhole pressure gauge (DHPG) that worked for only 90 days, during which it was possible to adequately establish a baseline well performance and accurate determination of formation damage (skin) and transmissibility. In July 2013, the well was shut in because of a stuck-closed subsurface safety valve (SSV). The well was back on line in 2014 after replacement of the upper completion, which included a new SSV and DHPG. Fig. 1 shows aspects of the well history.