Significance of Palygorskit in Drilling and Production of Hydrocarbon in Neogenes of North Kuwait
Mishra, Prasanta K.¹; Al Kandiri, Jaasim M.¹; Choudhary, Pradeep K.²; Hoppe, Markus³; Meadows, David³
¹Research and Technology, Kuwait Oil Company, Ahmadi, Kuwait.
²Field Development,HO, Kuwait Oil Company, AHMADI, Kuwait.
³Reservoir Petrography Team, Badely Ashton &Asociates, Winceby, United Kingdom.
Palygorskite is a fibrous authigenic clay mineral with the chemical composition of (Mg,Al)2Si4O10(OH).4(H2O), which forms mainly in coastal, schizohaline environments, under arid to semiarid climates. Recent studies have revealed that it occurs within the Neogene clastic rocks of the North Kuwait fields, where its fibrous pore-filling and dense mat-like grain-coating habit has previously sometimes been misinterpreted as a variation of fibrous illite.
SEM images of core plug samples from Neogene clastic reservoirs in the study area show the presence of abundant thin fibres within the pore systems, extending in all directions and locally blocking pore throats. EDX results have confirmed these as authigenic palygorskite. It is likely that these precipitates have a detrimental effect on the production from the affected reservoirs.
The palygorskite is frequently associated with corroded authigenic dolomite, which may have provided magnesium for the palygorskite formation, whilst the dissolution of detrital feldspar grains may be the source of silica and aluminium. Besides other expandable clay minerals, such as smectite and illite-smectite, which occur primarily within detrital clay throughout the Neogene succession, palygorskite is also believed to have some swelling potential. All these clays are thought to have the ability to swell as a result of contact with pore water, water-based drilling mud or during thermal production methods, resulting in potential formation damage.
The authigenic palygorskite occurs both within micro and macropore networks throughout the studied succession. The finely crystalline web-like and the fibrous pore-bridging habit displayed by this mineral is likely to reduce the permeability of the pore systems and can result in fines migration during production. The potential problems resulting from swelling and fines migration are more likely to be an issue in the southern part of the studied area where the overall content of the smectite, illite-smectite and palygorskite is higher compared to the northern areas. Considerable attention should be paid to the presence of palygorskite during the planning of field development techniques to avoid potential production problems.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012