Unconventional hydrocarbon resources: geological statistics, petrophysical characterization, and field development strategies

Abstract

Hydrocarbons exist in abundant quantity beneath the earth's surface. These hydrocarbons are generally classified as conventional and unconventional hydrocarbons depending upon their nature, geology, and exploitation procedure. Since the conventional hydrocarbons are under the depletion phase, the unconventional hydrocarbons have been a major candidate for current and future hydrocarbon production. Additionally, investment and research have increased significantly for its exploitation. Having the shift toward unconventional hydrocarbons, this study reviews in depth the technical aspects of unconventional hydrocarbons. This review brings together all the important aspects of unconventional reservoirs in single literature. This review at first highlights the worldwide unconventional hydrocarbon resources, their technical concept, distribution, and future supplies. A portion of this study also discusses the resources of progressive unconventional hydrocarbon candidates. Apart from this, this review also highlights the geological aspects of different unconventional hydrocarbon resources including tight, shale, and coalbed methane. The petrophysical behavior of such assists including the response to well logs and the discussion of improved correlation for petrophysical analysis is a significant part of this detailed study. The variation in geology and petrophysics of unconventional resources with conventional resources are also presented. In addition, the latest technologies for producing unconventional hydrocarbons ranging from fractured wells to different fluid injections are discussed in this study. In the end, the latest machine learning and optimization techniques have been discussed that aids in the optimized field development planning of unconventional reservoirs.

Prediction of gas production rate from shale gas reservoirs using a micro–macro analysis

“…Shales are the most common sedimentary rocks in the crust of the earth. Recent activities in shale gas exploration have shown that shale gas will be the most significant portion of the future global energy supply as traditional reserves begin to decline 1 – 4 . Improved reservoir conditions, advancement in horizontal drilling, and hydraulic fracking technology make shale gas extraction commercially feasible and successful 5 , 6 .…”

“…However, there is limited analysis of the flow rate and decline in production rate with time coupled with the pore structure of the shales. Besides the pore structures, facture length and initial pressures, other shale reservoir heterogeneities like components in shale (kerogen), adsorption/desorption in shale and pore fluid composition (dry gas) in shale can also influence the prediction of gas production 4,[16][17][18] .…”

Mechanisms in CO2-enhanced coalbed methane recovery process

“…Coalbed methane (CBM) is an important unconventional gas resource under development today (Muther et al, 2022). Nevertheless, 60% to 80% of the adsorbed CBM emits into atmosphere during coal mining (Prabu and Mallick, 2015;Serikov et al, 2022), creating explosion risks, which is traditionally diluted by ventilation.…”

Application of mathematical statistics to shale gas-bearing property evaluation and main controlling factor analysis

“…As an unconventional natural gas reservoir, shale can not only store free gas but can also adsorb gas 2 , 3 . Gas adsorption is an important property of shale reservoirs, and adsorbed and free gas fractions jointly largely account for the shale gas content and production 4 , 5 . Free gas is commonly distributed in large inorganic and organic pores and microcracks, whereas adsorbed gas generally occurs on the walls of organic pores and clay mineral pores with large specific surface areas 6 .…”