Simulation and evaluation method and system for under-salt dolomite water-rock reaction

Abstract

The invention provides a simulation and evaluation method and system for an under-salt dolomite water-rock reaction. The method comprises analyzing stratum water of a research area; stratum water classification is carried out by using a Sulin method; formulating experimental fluids, preparation of dolomite core sample, dolomite water rock reaction test is performed; the dolomite water-rock reaction is judged to reach chemical equilibrium; the method comprises the following steps: determining the fluid flow rate of the dolomite water rock reaction, carrying out the under-salt dolomite water rock reaction by using the prepared experimental fluid and a dolomite rock core sample, analyzing and calculating the changes of mineral components, corrosion and precipitation, and quantitatively evaluating the influence of the under-salt dolomite formation water on the corrosion and precipitation of the dolomite. According to the method, the quantitative evaluation of the reaction between the dolomite and the corresponding formation water under the geological background of the subsalt dolomite reservoir can be realized; the specific influence of stratum water attributes in the dolomite water-rock reaction process can be analyzed, control factors beneficial to formation and storage of under-salt dolomite pores are defined, and an analysis basis is provided for large-scale and efficient under-salt dolomite reservoir distribution and prediction.

Description

technical field [0001] The invention relates to the technical field of petroleum geological exploration, in particular to a method and system for simulating and evaluating the water-rock reaction of pre-salt dolomite. Background technique [0002] Pre-salt oil and gas resources, as an extremely important reserve growth point and strategic replacement area in the current world oil and gas industry, have shown huge exploration potential and good exploration prospects. [0003] Overseas, Brazil's deep-water pre-salt field has become a hot spot for overseas oil and gas exploration in recent years, and the Santos Basin is one of the oil and gas basins with the richest oil and gas resources in Brazil's sea area. In China, the pre-salt dolomite reservoirs in the Sichuan Basin are mainly distributed in the Sinian-Cambrian, and gas reservoirs of various sizes have been discovered. The pre-salt dolomite reservoirs in the Ordos Basin are mainly distributed in the Ordovician Majiagou F...

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Problems solved by technology

However, the pore types of dolomite samples are complex and diverse, including intercrystalline pores, oolitic mold pores, karst caves, cracks, etc. During the dissolution process, the pore structure often changes and forms a dominant channel for fluid migration, which will cause a change in the contact area between fluid and rock. change, leading to a decrease in the amount of rock dissolution, will inevitably affect the accurate understanding of temperature, pressure and fluid factors on the dissolution, and the water-rock reaction data of dolomite are not repeatable and reproducible

Chinese patent (publication number: CN105137033A) discloses a quantitative evaluation method and device for supergene karst effect of gypsum-carbonate reservoir, which only focuses on the dissolution effect and quantitative evaluation of gypsum-carbonate rock under supergene environment , is not applicable to the high temperature and high pressure conditions of dolomite water-rock reaction in the burial stage; although it considers the influence of the gypsum-salt composition in the rock sample on the dissolution, it ignores the formation water property factor. However, dolomite exists widely in the formation, and the fluid property is the key The key factors affecting the dissolution and precipitation of dolomite; the rock sample is soaked in the solution, the water-rock ratio and hydrodynamic mode do not conform to the underground reality, and the chemical connotation represented by the amount of rock dissolution is not clear

Yang Yunkun et al. (Re-understanding of deep dissolution of carbonate rocks based on in-situ observation of simulation experiments [J], Journal of Peking University (Natural Science Edition), 2014, 50(2): 316-322) based on this, the use of diamond pressure chambers (DAC) technology, designed a set of water-rock interaction simulation experiments with increasing buried depth for carbonate rocks. Although obvious cementation (precipitation) can be observed in situ, it cannot quantitatively analyze the dissolution of carbonate rock water-rock reaction. However, it is impossible to analyze the specific role of formation water properties in the water-rock reaction process of dolomites.

Fan Ming et al. (Reformation effect of acidic fluid on carbonate reservoir [J], Geochemistry, 2009, 38(1): 20-26) independently designed a carbonate rock dissolution rate tester, but the experimental device And experimental methods are dedicated to evaluating the dissolution rate of carbonate rocks, requiring that the water-rock reaction results of carbonate rocks are far from the chemical equilibrium. Due to the small amount of rock samples, the fluid generated by the reaction still has the ability to react with rocks, so it does not meet the requirements of underground water-rock reaction. The degree of water-rock reaction of dolomite should approximately meet the requirements of chemical equilibrium

In addition, the rock weighing method is used for the amount of carbonate rock dissolution, and it is impossible to determine which minerals are dissolved and which new minerals are precipitated in the water-rock reaction.

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