Identification, Origin and Distribution of Tarmats in Upper Zubair Sand Reservoir, Raudhatain Field, North Kuwait

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Upper Zubair Formation is a giant reservoir consisting of 350 ft of excellent quality sandstone. This main producing reservoir has a 100 thick tar mat historically encountered near oil water contact. Recently, a well completed in the crestal part of structure above tar mat zone and in good quality sand did not contribute to oil production and presence of tar was suspected. A re-look at identification, origin and distribution of the tar mat has become critical for formulating future development strategy of the reservoir.

Identification of Tar Mat in Zubair Formation of the X Oilfield, Southern Iraq

“…Micro-resistivity logs typically read a smaller value than deeper resistivity logs for oil zones drilled by mud filtrate, which had a lower salinity than formation water. In the tar zone, no mud filtrate can invade the formation around the borehole, so the micro-resistivity logs should have close or even greater resistivity than deeper resistivity logs (Azim et al, 2006). The thickness of tar mats was measured using this method for many wells in the X oil field oilfield showed in (Table 2) (Figs.…”

“…Numerous studies have been conducted on tar mats in the Zubair Formation. Azim et al (2006) studied the tar mat origin and distribution in the Raudhatain oilfield of north Kuwait in the Zubair Formation in the upper sand reservoir. The result showed that there is a 100 ft thickness of tar mats near the oil-water interface.…”

Identification of Heavy Oil (Tar Mats) Deposits and Forming Mechanism in the Main Pay of the Zubair Formation in North Rumaila Oil Field, Southern Iraq

“…Zubair sandstone reservoir has a variable thick Tar mat (asphaltic) interval near oil water contact and has an impact of the aquifer support of the reservoir. Tar mats are defined as zone of solid organic matter filling voids and fractures of rocks that can be laterally continuous and made a potential barrier to flow of fluid (Jacob, 1989).The Tar mat occurs in carbonate and sandstone petroleum reservoirs in many basins throughout the world (Wilhelm's and Larter, 1995).In the Zubair Formation in the Raudhatain oil field of north Kuwait was studied the origin and distribution of Tar mats (Azim et al, 2006), in Kuwait carbonate reservoir was investigated and modeled the Tar mats and their role in understanding oil reserves and recovery economics (Almansour, 2014), and in Saudi Arabia conducted an experimental study for enhancing the recover factor of Tar barrier and understand distribution of Tar mat (Alfayfi et al, 2015).Recently, the compiled wells in the upper sandstone member (main pay) of the Zubair reservoir in the flank parts of the structure did not significantly contribute to oil production due to the presence of Tar mat (specially at the DJ unit) so the aim of this study was to identify the Tar mat zones at these locations using full set of open hole logs, core, and cuttings descriptions in the eastern and western flanks and the possible mechanisms of Tar mat formation.…”