DHIs works well for de-risking prospectsFlat spot in Pliocene-Quaternary sediments. Image credit : Joshua Doubek, Wikipedia.

DHIs works well for de-risking prospects

According to a new report from Westwood, the use of DHI’s does improve the chance of making both technical and commercial discoveries. The method is particularly useful in frontier basins.

Flat spots are found to be the only Direct Hydrocarbon Indicators (DHI) that improve the all-over technical success rate, compared to other applied DHIs, according to a new report by the Westwood Global Energy Group.

Westwood has looked into 536 prospects with reported pre-drill support from DHIs, in 95 basins worldwide over the last 12 years (2008 – Q3 2019).

Exploration success rates for all wells with DHIs, compared to the benchmark average commercial success rate, in the period 2008 to Q3 2019. Figure: Westwood.

For flat spots, an increased commercial success rate of 39 per cent is observed, instead of the commercial success rate of 30 per cent for all exploration wells.

They also observed that DHI’s mainly improved the technical success rate, as in if there where hydrocarbons present or not in the prospect.

According to Westwood, prospects with other DHIs (Amplitude, AVO, Amplitude Conformance, & EM) were found to have below benchmark commercial success rates.

The exception being frontier plays, here DHIs proved to be effective. The success rates increased substantially in frontier plays, as shown in the lower figure.

In maturing and mature plays, the technical success rate was somewhat higher than average, but the commercial success rate was generally lover, 22 per cent compared to 28 per cent seen in the benchmark average.

Exploration success rates for wells drilled in frontier plays, by the five main DHI categories, and overall impact. Figure: Westwood.

Especially noted by Westwood, exploration in the UK, Norway and Australia saw particularly poor success rates from DHIs.

However, if you are hunting stratigraphic trap prospects, then DHIs significantly improve the performance of commercial success rate. But, AVO supported prospects perform below the average, pointing to a systemic misuse of this DHI.

Westwood also reports that the industry seems to have reduced the number of false positives and that in the last part of the period, 2014 – 2019, DHI success rate has increased.

Also, according to Westwood, the companies have learned that combining consistently well-conditioned seismic data with sound geological models is the key to applying DHIs effectively.

DHI

Direct hydrocarbon indicators (DHIs) are an anomalous type of seismic amplitude that may occur due to the presence of hydrocarbons.

They occur due to a change in pore fluids, which cause a change in the bulk rock’s elastic properties.

DHIs are mainly common in relatively young, unconsolidated siliciclastic sediments that have large impedance across lithologic boundaries.

They have various types of characteristics, which can be identified by the relationship between depth and acoustic impedance.

DHIs are used in hydrocarbon exploration wells, mainly to reduce the geological risks.

Source: https://wiki.seg.org/wiki/Direct_hydrocarbon_indicators 

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