Vertical transmissibility assessment from pressure transient analysis with integration of core data and its impact on wa

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ORIGINAL PAPER

Vertical transmissibility assessment from pressure transient analysis with integration of core data and its impact on water and miscible water-alternative-gas injections Mohammad Yunus Khan 1 & Ajay Mandal 2 Received: 6 December 2018 / Accepted: 18 February 2019 # Saudi Society for Geosciences 2019

Abstract The major key uncertainty of complex carbonate reservoirs are the vertical transmissibility across the tight dense (stylolite) layers and areal distribution of high permeability streaks (HKS), which have major impact on reservoir management, well locations, and well completion design in water and miscible water-alternative-gas (miscible WAG) injection process. The present study presents interpretation methodology of vertical transmissibility through assessment of horizontal to vertical permeability ratio (Kv/Kh) from various dynamic data. The Kv/Kh range assessment was done after integration with whole core data and pressure transient data. The impact of Kv/Kh on water and miscible WAG injection processes has also been investigated. The result shows that good vertical communication between the bulk of the porous sub-units and all across stylolite layers except one stylolite layer which acts as field wide barrier. In addition, simulation result of water and miscible WAG injection with higher order of estimated Kv/Kh ratio (0.2 to 1 as found in good permeability porous layers of most of the carbonate reservoirs) indicates no major impact on water cut (WCT), gas oil ratio (GOR), water breakthrough (WBT), gas breakthrough (GBT), and expected ultimate recovery (EUR) in homogeneous area, while oil recovery acceleration with lower WCT/GOR and slightly early WBT/GBT time in heterogeneous area due to gravity or viscous effect suppressed by heterogeneity effect. However, the lower order of Kv/Kh ratio (~ < 0.05) provide delay in WBT/GBT and lower WCT / GOR production due to viscous dominant flow which results in lower gravityviscous number. Keywords Kv/Kh ratio . Anisotropy assessment . Pressure transient analysis . Miscible WAG . Reservoir simulation model . Stylolite layer . Carbonate reservoir

Introduction The permeability anisotropy ratio (Kv/Kh) has significant impact on hydrocarbon recovery, sweep efficiency, productivity, well completion design, gas/water coning, well testing, enhanced oil recovery, reservoir management, and reservoir development strategy as well as the productivity of horizontal and multilateral wells in water and WAG injection processes (Landrum and Crawford 1960; Masalmeh et al. 2010; Mohamed et al. 2011). Editorial handling: Ray Rui * Ajay Mandal [email protected] 1

Kuwait Oil Company-KOC, Al Ahmadi, Kuwait

2

Indian Institute of Technology (ISM), Dhanbad, India

However, the variation of Kh and Kv of carbonate reservoir effects on water/WAG flood’s efficiency are due to channeling of the solvent through high permeability regions, which reduce the storage and displacement efficiency of the displacing solvent (Wu et al. 2004). While capillary force, viscous force, gravity for