Water Flooding Optimization for a Super-Giant Carbonate with Thief Zones

Wei, Chenji; Li, Yong; Li, Baozhu; Yinxi, Wang; Kaiping, Cai; Zhang, Qi; Zhou, Jia‐Xi

doi:10.2118/175669-ms

Cited by 4 publications

References 11 publications

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Middle Eastern carbonate reservoirs – the critical impact of discrete zones of elevated permeability on reservoir performance

Cross,

Burchette

2024

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Middle Eastern carbonate petroleum reservoirs exhibit a range of heterogeneities which consist of variable combinations of primary stratigraphic and secondary diagenetic and structural characteristics. These produce diverse permeability architectures which can exert a profound influence on reservoir performance during secondary recovery. Of particular importance are laterally persistent discrete zones of elevated permeability (DZEP) that typically make up a volumetrically minor proportion of the reservoir yet show disproportionately high fluid inflow or outflow. The stratigraphic, diagenetic, and structural origins of elevated permeability in Middle Eastern carbonate reservoirs are considered here and the consequences of such features for reservoir performance are discussed. The term DZEP denotes geological sources of elevated permeability at least an order of magnitude greater than background reservoir properties. Stratigraphically organised DZEP comprise coarse-grained layers, event beds or parasequence tops or bases in neritic or platform interior settings. Other origins include bioturbated layers, grainy clinothems, and bed-scale, grain-size variations in shoal deposits. Diagenetic DZEP are typically dissolution horizons with mouldic and touching-vug pore networks or dolomitized intervals which often overprint stratigraphic DZEP. Structural DZEP include individual faults, fracture corridors, and fracture concentrations related to mechanical stratigraphy. During production through natural pressure depletion, DZEP may dominate well productivity. Under secondary recovery, the same intervals may dominate inter-well fluid flow, causing flood conformance issues, cross-zone fluid movement, bypassed pay, and earlier-than-expected water or gas breakthrough to production wells. Optimisation of production and ultimate recovery relies on collecting the correct kinds of data at a sufficiently early stage in the reservoir characterisation process to permit their inclusion in static and dynamic reservoir models.

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Middle Eastern carbonate reservoirs – the critical impact of discrete zones of elevated permeability on reservoir performance

Cross,

Burchette

2024

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Thief Zone Characterization and its Impact on Well Performance Based on Surveillance Data, Experimental Data and Theoretical Analysis for a Carbonate Reservoir

Wei

Zheng

Ouyang

et al. 2019

Day 3 Thu, September 19, 2019

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Understanding the heterogeneity is critical for a successful water injection in a carbonate reservoir. Thief zone is one of the most obvious forms of heterogeneity, which indicates the thin layer with higher permeability compared to the average reservoir permeability. The existence of thief zone results in earlier water breakthrough and faster water cut increase, which then lead to lower sweep efficiency and smaller recovery factor. Therefore, determining the distribution of thief zone and its impact towards production, and proposing a corresponding development plan are very important. In this paper, a novel method is established to determine the thief zone distribution based on dynamic surveillance data. A new index is proposed as the relative contribution index to characterize the relative contribution of a certain layer, which is fundamental for thief zone determination. In addition, effect on water flooding development of thief zone's location is studied by experimental and theoretical analysis. The changes of water cut and production rate are analyzed under different conditions such as location of the thief zone, injection rate, and variogram. Finally, optimized development strategy is proposed to deal with the existence of thief zone. Distribution of thief zone is characterized based on the proposed method, which indicates that thief zone development has intimate relationship with depositional facies and diagenesis. Experimental and theoretical analysis results show that the present model considering stratified water-flood is consistent with the experimental results. The water displacement effect is the best when the thief zone is located in the upper reservoir. This paper also points out the optimal adjustment period for water shutoff and profile control of the reservoir with thief zones. In addition, the greater the injection rate, the faster the water cut increase. Furthermore, the smaller the variogram, the slower the water cut increase, and the later the water breakthrough time. This study provides a method to characterize thief zone, which can be used as a reference for similar oilfield development. In addition, it provides a quick and reasonable guide in the later adjustment of water flooding development of carbonate reservoirs with thief zones.

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A Novel Correction Method for Pressure Transient Analysis Results of Horizontal Wells in Stratified Carbonate Reservoir with High Permeability Zone

Zhao

et al. 2022

SPE Annual Technical Conference and Exhibition

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High permeability zone (HPZ) formed by sedimentation and diagenesis has been founded in numerous oil fields in Middle East. Meanwhile, horizontal well have been applied universally in these oil fields. To obtain wellbore status and reservoir properties, pressure transient analysis (PTA) is a convenient and economic surveillance method. However, when it comes to stratified reservoir, heterogeneity between layers should be noticed. Log-log plot of actual data will be far form ideal analytical solution with homogeneous hypothesis. Therefore, the interpreted results would not be representative for wellbore and reservoir condition. In this research, we proposed a novel correction mathematical model and correction workflow for PTA results of horizontal wells in stratified carbonate reservoir with HPZ. This research innovatively imports production performance analysis and other monitoring methods to PTA in the view of flow field. This new approach holds favorable potential to provide accurate wellbore status and reservoir parameters for making the most use of surveillance budget.

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Water Flooding Optimization for a Super-Giant Carbonate with Thief Zones

Cited by 4 publications

References 11 publications

Middle Eastern carbonate reservoirs – the critical impact of discrete zones of elevated permeability on reservoir performance

Middle Eastern carbonate reservoirs – the critical impact of discrete zones of elevated permeability on reservoir performance

Thief Zone Characterization and its Impact on Well Performance Based on Surveillance Data, Experimental Data and Theoretical Analysis for a Carbonate Reservoir

A Novel Correction Method for Pressure Transient Analysis Results of Horizontal Wells in Stratified Carbonate Reservoir with High Permeability Zone

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