Oilfield Water and Favorable Petroleum Exploration Targets for the Triassic Baikouquan Formation in the Slope of Mahu Depression, Junggar Basin

Huifei Tao,Tao Wu,Yongqiang Qu,Bingbing Liu,Lei Wang

doi:10.1155/2021/6699489

Huifei Tao, Tao Wu + Show 3 more

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https://doi.org/10.1155/2021/6699489

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Abstract

In this paper, we attempt to clarify the relationships between oilfield water and hydrocarbon distribution of the Triassic Baikouquan Formation, in the slope zone of Mahu depression, Junggar Basin, NW China, based on oilfield water mineralization degrees, diagenesis analysis, formation pressure coefficients, burial history, and thermal evolution processes. The results show that the study area can be divided into four zones according to the mineralization degrees, that is, (1) zone I: NaHCO3 + Na2SO4 type water with residual intergranular pores, porosity usually higher than 10%. The strata of zone I are generally buried shallow and influenced by leaching from atmospheric precipitation. This area contains normal edge and bottom water and has normal formation pressure coefficients (average 1.12); (2) zone II: CaCl2 type water with mainly compaction diagenesis, porosity usually less than 7% and high formation pressure coefficients (average 1.41); (3) zone III: NaHCO3 + CaCl2 type oilfield water with mainly feldspar dissolution diagenesis, porosity usually greater than 9% and high formation pressure coefficients (average 1.53); and (4) zone IV: CaCl2 type water, mainly compacted diagenesis with a few intergranular and feldspar dissolved pores, and high formation pressure coefficients (average 1.58). The mineralization degrees of the oilfield water in zone II, III, and IV are relatively high. The appearance of NaHCO3 type water in the deeply buried areas is usually related to oil and gas charging. Therefore, within the strata, deeply-buried areas (e.g., zone III), where NaHCO3 type water has been developed, are favorable targets for oil and gas exploration.

Highlights

Oilfield water is an important part of the fluid system in oil and gas reservoirs
The mineralization degrees from the northern edge to the slope and center of the depression are average values of 3000 mg/L, 8000 mg/L, 10000 mg/L, to 15000 mg/L, the study area is divided into four zones (I, II, III, and IV)
The CaCl2 + NaHCO3 type oilfield water is developed in zone III

Summary

Introduction

Oilfield water is an important part of the fluid system in oil and gas reservoirs. Its formation and movement are closely related to oil and gas generation and migration, as well as to the formation, preservation, and destruction of the oil or gas reservoir [1,2,3,4,5]. Researchers can assess the migration, accumulation, and preservation conditions of the oil and gas according to the hydrochemical data obtained from the water [7, 8]. According to the classification scheme of Suling, oilfield water usually is divided into four types: sodium sulfate (Na2SO4) type, sodium bicarbonate (NaHCO3) type, magnesium chloride (MgCl2) type, and calcium chloride (CaCl2) type [9]. With buried depth increasing of the strata, the water type becomes magnesium chloride type and calcium chloride type [9]

Results

Discussion

Conclusion