There are a lot of sludge generated in oil production and storage processes, usually complicated chemical processes are involved to treat the sludge effectively, and high cost and environmental pollution are always extremely heavy burden for Liaohe Oilfield. Therefore, the feasibility and performance of sludge injection into steam stimulated wells, and sludge sequestration and associated heavy oil recovery improvement are investigated based on results of lab research and field operation.
At first, the composition and rheology of the sludge samples from Liaohe Oilfield are measured and analyzed in detail. Secondly, the injection, sequestration and block performance are investigated by sand pack experiments, particularly the aggregation and blocked sand are analysed by scanning electron microscope, and improvement of heavy oil recovery by sludge injection. Thirdly, the principles of sludge sequestration and associated heavy oil recovery improvement are discussed. At last, field application of sludge in Liaohe Oilfield is presented.
As we know, the sludge are produced from the reservoir, it is comprised of mud, fine sand, some oil phase components and water. Aggregation of the sludge components except water is potential to block porous media such as produced formation, at the same time, the sludge are buried in its origin, the reservoir. The sludge is injected to produced reservoir through enlarged pore at high injection pressure, and aggregated mud, fine sand and oil from sludge could consolidate formation sand and block pores effectively after injection process (permeability decease of sludge blocked sand tube is more than 90%). As a result, the sludge is stored in steamed formation, and separated water could be filtered and produced. At the same time, steam conformance could be improved by stored sludge, accordingly heavy oil production is increased. Average oil production increase of 45 wells in Liaohe Oilfield is more than 20%.
Substantial sludge are treated by such subsurface sludge sequestration in steamed heavy oil reservoir, and sludge sequestration in other reservoirs are evaluating as well.