1st Research Conference - Gulf Coast Section SEPM
1st Research Conference - Gulf Coast Section SEPM
1st Research Conference - Gulf Coast Section SEPM
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Fluid System Compositions: Drilling, completion, and enhanced recovery<br />
fluids react with natural (authigenic) cements in rock pores and these reactions<br />
can affect the quality and production of any reservoir. This effect is particularly<br />
true in the Woodbine in East Texas where a wide variety of natural cements are<br />
present (Fig. 2). In some locations, Woodbine sandstones are sensitive to fresh<br />
or sodium-based drilling and completion fluids because of the presence of the<br />
swelling clays illite-smectite or smectite. In other areas these clays are absent<br />
and no swelling problems exist. Certain areas are characterized by sensitivity<br />
to either HCl or HF acids (whether used in mud clean-up or stimulation) due to<br />
the presence of specific sulfides or oxides in the pore systems. The sensitivities<br />
of Woodbine sandstones to waters and acids are not uniform across East Texas<br />
but vary from area to area and from zone to zone. Thus drilling and completion<br />
fluids should be designed on a local regional scale.<br />
Drlll Stem testing Results: Diagensis can have a significant effect on drill<br />
stem testing results. The presence of authigenic cements often causes poor drill<br />
stem test results. There are instances when DST results should be ignored and<br />
well completion encouraged. Poor DST's in the Woodbine result from any or all<br />
of the following: (1) secondary porosity, (2) silica overgrowths [Fig. 2A], and (3)