Enhanced Bioturbated Sandstones Reservoir Evaluation and Characterization: An Insight from Baram Delta
Authors: Trianto A. , Wan Sagar S. F. S. , Kasim F. H. , Hendraningrat L. , Ramly N. A. , Rasid S. A. A. , Bannu S. , Sedaralit M. F. 
Published: October 2023

Bioturbation is the disturbance of sediment layers by biological activity and is a significant process in deltaic environment. Bioturbation is an important source of reservoir heterogeneity and has an impact on rock properties such as porosity and permeability and their distribution. During logging operation, varying intensity levels of bioturbation activity may alter the response of the tool hence leading to misinterpretation of the formation petrophysical properties. In this paper, a technology called H-FABS (Hasani-Faizal Adi Budi Souvick/Sarah) Graph was developed to enhance in characterizing a reservoir by differentiating between bioturbated and non-bioturbated sand and to identify opportunities behind the casing.

Two pilot fields in Baram Delta have been chosen as field trials because its deposition environment is suitable and expected to have high bioturbation activity. In total, 5 wells were shortlisted as pilots from both fields. The integrated approach workflow is divided into 6 (six) levels to deploy the technology: Screening, Well ranking, Well integrity analysis, Reservoir analysis, Engineering detail, and Value creation, respectively. The laboratory study used core to determine the bioturbation interval and assigned the value of the bioturbation. intensity. The well data at the same depth as the core was then plotted into the H-FABS graph to check where the points were located. The interval with high bioturbation intensity will be checked with petrophysical properties and reservoir dynamic data to determine the current fluid type. Then the wells will be ranked based on data in H-FABS graph as well as current production data and well integrity issue. If the current fluid type is oil, add perforation activity can be done as an extra to the technology, and value creation can be investigated.

Enhanced Bioturbation technology pilot fields have improved understanding of bioturbated zones and enable prediction for these zones. It identified the value creations. First, bioturbation analysis also helps to enhance geologic understanding and overall reservoir characterizations of bioturbated reservoirs. Second, it can also identify potentially located bypass oil due to underestimate petrophysical properties such as porosity, permeability, and water saturation, identifying un-risked upside potential of pilot fields from bioturbated reservoirs. Post bioturbation tool screening activities, eight wells were identified as potential bioturbation add-perforation candidates. Third, additional oil reserves from behind casing opportunity with estimated &gt; 2 MMSTB, from 5 wells of 2 Fields.

This paper provides identifications of un-risked upside potential in Pilot fields. In addition, it is an innovative well-screening technique to identify bypassed hydrocarbon opportunities. The opportunity behind casing that can add more oil reserves could be selected through significant efficiency gain in well screening methods.