The Anatomy of Bypassed Low Resistivity Low Contrast Hydrocarbon Reservoirs: The Arts of Finding Additional Barrels in a Highly Complex Stratigraphic Geological Setting
Authors: Zulkipli Siti Najmi , Harun Norhana 
Published: October 2019

Maximizing production and sustaining the barrels produced is the aspiration to all oil and gas key players. Current producing reservoirs may not giving good yield till the end of expected production life due to depletion, high water cut and also due to well integrity issues. Finding prolific reservoirs with thick pay zones and excellent rock quality are also becoming scarcer as more complex reservoir characterization comes into play. The challenges are further compounded by high uncertainty in distinguishing hydrocarbon fluid type. Hence, a systematic effort need to be garnered to sustain the production pipeline. This paper will present several case studies and petrophysical solutions in monetizing the untapped low resistivity low contrast reservoirs in a highly complex stratigraphic trap geological setting to squeeze more barrels into production as well as adding value to the reserves portfolio.

Identifying the low resistivity and low contrast (LRLC) reservoirs starts with delineating the log responses complemented by other subsurface data such as mud log, cores, fluid samples and advanced acoustic logging to determine lateral sand continuity. Often, well test and production data is used as the benchmark to identify hydrocarbon fluid type in the contradicting evidences. Comparison of nearby wells performance and evaluating fluid contact movement will be also part of the assessment stage. Application of in-house reservoir enhancement modeling (REM) will be the highlight of this paper to reveal those new promising reserves which are masked by thin laminated sand, low salinity, presence of light oil with similar log responses as gas and high silt content. Few examples relating the well production performance with log characteristics will be also discussed in this paper.

Results proved that production gain has soared up to 4800 bopd in total to make an astounding impact to the overall field production scenario. In few cases, significant new reserves addition is recorded which further open-up new upside opportunities for work-over, more aggressive production enhancement, appraisal and development drilling campaign. A systematic formation evaluation and petrophysical workflow has also been established to mature and realize the gain which sets a replication standard to the entire region. As more data comes in from the actual jobs done, a database relating the log responses with production capacity and catalogue of past job lessons learned have been initiated for future reference and demonstrating concrete evidences in realizing LRLC potential.

In a nutshell, exploiting LRLC potential in complex stratigraphic play requires an intensive subsurface evaluation and offers a promising opportunity in expanding the resource base and generating the cash. The efforts must continue with more success being replicated and bringing in more technology to minimize LRLC uncertainty and create a chain impact to production growth.