Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (3): 690-701.doi: 10.11743/ogg20210314

• Methods and Technologies • Previous Articles     Next Articles

Prediction of burial dissolved vugs in carbonates based on dissolution simulation: A case study of the Longwangmiao Formation dolostone reservoirs, Sichuan Basin

Anjiang Shen1,2(), Zhanfeng Qiao1,2, Min She1,2, Shaoxing Meng1,2, Jie Zhang1,2, Xin Wang1,2   

  1. 1. Hangzhou Research Institute of Geology, PetroChina, Hangzhou, Zhejiang 310023 China
    2. Key Laboratory of Carbonate reservoirs, CNPC, Hangzhou, Zhejiang 310023, China
  • Received:2020-07-09 Online:2021-06-28 Published:2021-06-23

Abstract:

The prediction of burial dissolved vug distribution in carbonate rocks has always been challenging.This study, taking the Longwangmiao Formation dolostone as an example, reveals the origin of burial dissolved vugs and their distribution in carbonates through dissolution modelling under formation conditions and may serve as a theoretical foundation for the prediction of burial porosity in carbonates.The results show that the burial dissolved vugs in carbonates are formed under the control of the physical properties of rocks, organic acid concentration and temperature.Their distribution is laterally conditioned by geological boundaries (namely, exposed interface, sequence boundary, unconformity and fault system) and high-permeability layers, and vertically showing a vug-generating peak season, during which, burial dissolved vugs occurred in great numbers because of suitable temperature and high concentration of acid fluid at some intervals with certain burial depth and then evolved along with burial, temperature-pressure and fluid changes.Based on the understanding of the origin of burial dissolved vugs and their distribution patterns, this study quantitatively predicts the burial dissolved vug distribution in the Longwangmiao Formation dolostone by mapping the pre-burial porosity distribution of the Longwangmiao Formation, the organic acid and hydrocarbon generation intensity of the Qiongzhusi Formation source rocks at the temperature window of 70-100 ℃, the distribution of paleo-uplifts and faults as well as the burial duration of the Longwangmiao Formation within the window (70-100 ℃, corresponding to a depth of 1 740-2 850 m).This technique and process may be a useful tool in the prediction and assessment of burial dissolved vugs in other carbonate reservoirs.

Key words: burial dissolved vug, vug-generating peak season, dissolution modelling, dolomite reservoir, Longwangmiao Formation, Sichuan Basin

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