Characterization of flow units, rock and pore types for Mishrif Reservoir in West Qurna oilfield, Southern Iraq by using lithofacies data

Abstract

This study has been accomplished by testing three different models to determine rocks type, pore throat radius, and flow units for Mishrif Formation in West Qurna oilfield in Southern Iraq based on Mishrif full diameter cores from 20 wells. The three models that were used in this study were Lucia rocks type classification, Winland plot was utilized to determine the pore throat radius depending on the mercury injection test (r35), and (FZI) concepts to identify flow units which enabled us to recognize the differences between Mishrif units in these three categories. The study of pore characteristics is very significant in reservoir evaluation. It controls the storage mechanism and reservoir fluid properties of the permeable units while pore structure is a critical controlling factor for the petrophysical properties and multiphase-flow characteristics in reservoir rocks. Flow zone indicator (FZI) has been used to identify the hydraulic flow units approach (HFUs). Each (HFU) was reproduced by certain FZI and was supposed to have similar geological and petrophysical properties. The samples were from four lithofacies, mA, CRII, mB1, and mB2. Because of the wide range of cored-wells samples (20 wells), this paper is updated the previous studies and indicated some differences in the resulting categories. It was noticed as results of this study that the rocks types of the lower Mishrif were mostly ranged from wackestone to packstone in the upper part of mB2 which reflected mid-ramp facies while the upper part of mB2 referred to shoal facies and for the mB1 unit the rocks types mostly range from packstone to grainstone with some points as wackestone marked as shoal and rudist bioherm facies. Grainstone relatively decreases with the increasing of depth from upper to lower Mishrif while wackestone and packstone indicated increasing in the same direction. The unit mA is marked as mesopores and macropores, while megapores and macropores feature increased in mB1 which has been noticed in the northern part of West Qurna oilfield due to increasing shoal and rudist bioherm facies, the mB2 unit revealed increasing in mesoporous and decreasing in megaporous. The upper Mishrif (mA) has three flow units, while the lower Mishrif (mB1, mB2) has eight flow units four for each reservoir unit.

Effect of Heterogeneity on Recovery Factor for Carbonate Reservoirs. A Case Study for Mishrif Formation in West Qurna Oilfield, Southern Iraq

“…(mB1 and mB2) which represents the lower part of the Mishrif varies from observed sharp heterogeneity in the mB1 unit to the minimal heterogeneity in the lower part of the mB2 unit Fig. 3 [35]. Fig.…”

“…The mA Unit has a set of rock types consequent to facies ranging by different degrees of superficial facies in the upper formation of the mA unit. The mA unit contains a three-flow unit, while the lower Mishrif has eight flow units [35,41]. The Mishrif formation is a bit of a secondform regulation trajectory of Arabian massive gradation, which is identified as (AP8) [42,43].…”

“…Numbers and Source of Plugs used in this Study[35] Shows Significant heterogeneity in CRI, CRII, mB1, and lower mC, some heterogeneity in mA, and relatively homogeneous in mB2U, mB2L, and upper mC.…”

Effect of Heterogeneity on Capillary Pressure and Relative Permeability Curves in Carbonate Reservoirs. A Case Study for Mishrif Formation in West Qurna/1 Oilfield, Iraq

“…Mishrif Formation holds an irregular quality and heterogeneous reservoir properties by the effect of the depositional cycles and the sequence stratigraphic. Rocks porosity ranges from high porous (more than 20%) to low (5-10%) [33], the heterogeneity effect is very clear in variable permeability anisotropy values, in which the mb1 unit indicates more than the heterogeneity of the others [34].…”

A new approach to predict carbonate lithology from well logs: A case study of the Kometan formation in northern Iraq

“…The lithology of carbonate successions governs the heterogeneity of petrophysical characteristics such as porosity and permeability. Thus, a precise understanding of the spatial and vertical lithological variations is critical for adequate characterization of the petrophysical and mechanical properties of carbonate reservoirs [ [1] , [2] , [3] , [4] ]. Lithology parameters largely control the rock density, strength properties of the rock [ [5] , [6] , [7] ], and hydraulic fracturing [ 8 ].…”