Use of Cluster Analysis to Group Organic Shale Gas Rocks by Hydrocarbon Generation Zones

Tadeusz Kwilosz,Mariusz Miziołek,Bogdan Filar

doi:10.3390/en15041464

Tadeusz Kwilosz, Mariusz Miziołek + Show 1 more

Open Access

https://doi.org/10.3390/en15041464

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Journal: Energies	Publication Date: Feb 17, 2022
Citations: 1	License type: CC BY 4.0

Affiliation: Oil and Gas Institute - National Research Institute

Abstract

In the last decade, exploration for unconventional hydrocarbon (shale gas) reservoirs has been carried out in Poland. The drilling of wells in prospective shale gas areas supplies numerous physicochemical measurements from rock and reservoir fluid samples. The objective of this paper is to present the method that has been developed for finding similarities between individual geological structures in terms of their hydrocarbon generation properties and hydrocarbon resources. The measurements and geochemical investigations of six wells located in the Ordovician, Silurian, and Cambrian formations of the Polish part of the East European Platform are used. Cluster analysis is used to compare and classify objects described by multiple attributes. The focus is on the issue of generating clusters that group samples within the gas, condensate, and oil windows. The vitrinite reflectance value (Ro) is adopted as the criterion for classifying individual samples into the respective windows. An additional issue was determining other characteristic geochemical properties of the samples classified into the selected clusters. Two variants of cluster analysis are applied—the furthest neighbor method and Ward’s method—which resulted in 10 and 11 clusters, respectively. Particular attention was paid to the mean Ro values (within each cluster), allowing the classification of samples from a given cluster into one of the windows (gas, condensate, or oil). Using these methods, the samples were effectively classified into individual windows, and their percentage share within the Silurian, Ordovician, and Cambrian units is determined.

Highlights

Received: 3 January 2022In nature, there are no two identical natural gas and crude oil reservoirs
The results presented in this article, obtained through methods using artificial intelligence, may be a valuable supplement to these results [29]
total organic carbon (TOC) (% by weight); the temperature at which the maximum quantity of hydrocarbons is produced during kerogen cracking Tmax (◦ C); free hydrocarbon content S1; the amount of hydrocarbons released during kerogen cracking S2; hydrogen index HI; oxygen index OI; and vitrinite reflectance Ro (%).The parameters listed are from the Rock-Eval pyrolysis analysis with the exception of Ro

Summary

Introduction

Received: 3 January 2022In nature, there are no two identical natural gas and crude oil reservoirs. All natural gas reservoirs can be divided into two groups: Accepted: 11 February 2022. Conventional (traditional) reservoirs, unconventional reservoirs [1]. The classification of a reservoir as belonging to a specific group requires adopting selection criteria. Because the profitability of an investment depends largely on the income from gas sales, the primary selection criterion is the permeability of reservoir rock, since it directly affects the well output. It has been assumed that reservoirs with permeability exceeding 0.1–0.5 mD are categorized as conventional reservoirs. The remaining reservoirs are in turn included in the group of unconventional reservoirs. The group of unconventional reservoirs can be divided into the following types of reservoirs: tight gas, shale gas, gas reservoirs in coal seams, reservoirs of gas trapped in hydrates [2]

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