ENHANCED OIL RECOVERY (EOR)

There are distinct phases in the life of every oil and gas well that is drilled.  When a well is first drilled, pressure depletion and gravity drive deliver the oil to the surface.  During this phase anywhere from 10 to 35% of
the original oil in place will be recovered.  

Once the well pressure drops due to the gas cap being blown down, the ability of the formation to move a heavy column of oil and or water to the surface becomes severely diminished.  At this point in times Oil and Gas companies are faced with the challenge of extending the life of the field.  Many factors affect the method employed to enhance the recovery of the oil left in place after the Primary Recovery phase is over.

Water flooding and thermal techniques such as hot water and steam flooding account for 40% of the Enhanced Oil Recovery production in the United States. Other methods include chemical and CO2 flooding.  In
formations that produce sufficient amounts of saltwater in addition to oil,
there exists the opportunity to re‐inject the produced formation water into
injection wells, driving displaced, stranded oil into the producing
wellbores.  Injected water also helps to increase depleted reservoir pressures and, the risk of formation damage is minimal, as the water and the rock are highly compatible. When utilizing the proper EOR strategy,
companies can expect to recover up to an additional 50% of the oil left in
place after the primary recovery phase of production.  

The field is 64,000
acres in the northern part of Caddo Parish, Louisiana and is flanked to the
west by Caddo Lake and to the east by the Red River. There have been over
35,000 producing wells drilled which have produced over four hundred million
barrels of oil. It sits on top of the Sabine uplift, which is the stratagraphic
uplift structure common to Northern Louisiana. Due to the uplift, many of the
formations became excellent reservoir rock for hydrocarbons. Impervious
formations called “cap rocks” create traps that allow the oil and gas to
accumulate beneath them under great pressure.



The field produces oil and gas from multiple
zones from the shallow Annona Chalk formation (1350’ – 1600’) to the Cotton
Valley Formation (10,000’ – 12,000’). The Annona Chalk is a limestone formation with matrix porosity. The
porosity within the matrix ranges from 23% to 27%, but the formation is very
tight. The chalk has massive reserves with the production zone ranging from 150
to 250 foot thickness. The chalk has produced approximately 6 % of total
contained reserves. The depth of the Annona formation ranges on average from
1400 feet to 1700 feet from the surface. The type of oil is paraffin based with
a gravity ranging from 42 to 44.The wells in the Caddo Pine Island Field, for
the most part, are considered stripper wells and qualify for preferential tax
treatment in the United States.