Driving forces and their relative contributions to hydrocarbon expulsion from deep source rocks: A case of the Cambrian source rocks in the Tarim Basin

To thoroughly understand the dynamic mechanism of hydrocarbon expulsion from deep source rocks, in this study, five types of hydrocarbon expulsion dynamics (thermal expansion, hydrocarbon diffusion, compaction, product volume expansion, and capillary pressure difference (CPD)) are studied. A model is proposed herein to evaluate the relative contribution of different dynamics for hydrocarbon expulsion using the principle of mass balance, and the model has been applied to the Cambrian source rocks in the Tarim Basin. The evaluation results show that during hydrocarbon expulsion from the source rocks, the relative contribution of CPD is the largest (>50%), followed by compaction (10%-40%), product volume expansion (5%-30%), and thermal expansion (2%-20%). The relative contribution of diffusion to hy-drocarbon expulsion is minimal (<10%). These results demonstrate that CPD plays an important role in the hydrocarbon expulsion process of deep source rocks. The hydrocarbon expulsion process of source rocks can be categorized into three stages based on the contribution of different dynamics to the process: the first stage is dominated by compaction and diffusion to expel hydrocarbons, the second stage is dominated by product volume expansion and CPD, and the third stage is dominated by product volume expansion and CPD. This research offers new insights into hydrocarbon exploration in tight oil and gas reservoirs.(c) 2022 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Automated summary

In this study, five types of hydrocarbon expulsion dynamics were studied to understand the mechanism of hydrocarbon expulsion from deep source rocks. A model was proposed to evaluate the relative contribution of different dynamics using mass balance principle, and it was applied to Cambrian source rocks in the Tarim Basin. The results showed that capillary pressure difference (CPD) had the largest contribution (>50%), followed by compaction, product volume expansion, and thermal expansion. Diffusion had minimal contribution. The research categorized the hydrocarbon expulsion process into three stages based on the dominant dynamics, providing insights for hydrocarbon exploration in tight oil and gas reservoirs.