Relating seismic interpretation to reserve/resource calculations: Insights from a DHI consortium

Abstract

In the process of quantifying resources/reserves, geoscientists attempt to employ all the available pertinent information to produce the most accurate results. The presence of direct hydrocarbon indicators (DHI) on seismic data can have a significant impact on the reserve/resource calculations not only for volumes, but also uncertainty levels. In 2001 a consortium of oil companies was organized in an attempt to understand seismic amplitude anomalies interpreted as DHIs and their impact on prospect risking and resource calculations (Roden et al., 2005; Forrest et al., 2010). The geologic setting, seismic and rock physics data quality, DHI characteristics, and calibration of drilling results are all incorporated into a database in a consistent and systematic process. From this process, the evaluation of 217 prospects and associated well results has enabled an in-depth understanding of the relevant key aspects of seismic amplitude anomalies and how they relate to drilling results.

Explainable Machine Learning for Hydrocarbon Prospect Risking

“…Specifically, the presence of seismic amplitude anomalies interpreted as direct hydrocarbon indicators (DHIs) can significantly bias interpreters to predict higher chances of success for high risk prospects and not predict high enough chances of success for prospects with numerous positive DHI characteristics. The DHI Consortium set up in 2001 collected a prospect database contributed to by over 85 companies (H.Pettingill, personal communication, 2022) with the aim to systematically understand the significance of various seismic amplitude anomalies as DHIs (Roden et al, 2012). A comprehensive knowledge base was developed where information related to geologic settings, seismic and rock physics data quality, DHI characteristics, and calibration of drilling results was all incorporated into one central library of drilled prospects.…”

“…The result is a comprehensive evaluation system that thoroughly incorporates information from all modalities in an objective manner to arrive at a probability of success for the prospect of interest. The process is outlined in Figure 1 and described in Roden et al (2012). A major goal of interest to geophysicists is to understand how various seismic amplitude anomalies impact the risking process.…”

“…A major goal of interest to geophysicists is to understand how various seismic amplitude anomalies impact the risking process. By statistically correlating individual attributes to post-drill results in a database of drilled prospects, Roden et al (2012) generated attribute importance rankings for both class 3 and class 2 wells. Amplitude downdip conformance (see Figure 2) and amplitude consistency in the mapped target area were identified to be important attributes across both classes.…”

Post-drill geophysical characterization of two deep-water wells of Cauvery Basin, East Coast of India

“…While evaluating Direct Hydrocarbon Indicator (DHI) characteristics, an understanding of geological setting is crucial as an expected DHI response is dependent on it. The presence of a DHI in seismic data aids in de-risking of a prospect and has a significant impact on reserve calculation (Hilterman 2001;Roden et al 2005Roden et al , 2012Hanafy et al 2018). AVO analysis is a deterministic way to predict hydrocarbon presence from seismic data (Smith and Gidlow 1987;Rutherford and Williams 1989;Hilterman 1990;Castagna and Smith 1994;Smith and Sutherland 1996;Castagna et al 1998;Figueiredo et al 2019;Fawad et al 2020).…”