Some Illinois reservoirs are present in dolomite. This rock is analogous to limestone but has long been chemically altered. The limestone has been recrystalized to kind high-quality-grained dolomite, a approach that could dissolve fossils and limestone to sort huge and little holes (pores) that will hold oil. Connect, understand, and http://wellsite-geology28272.get-blogging.com/953216/the-best-side-of-oilfield-geology