Abstract
The Kenkiyak pre-salt oil field is a heavy oil reservoir with the average porosity of 36.6%, the average permeability around 1875x10−3μm2, the buried depth between 290∼380 m, the dead oil viscosity within 144∼691mPa.s @20°C, the reservoir temperatures between 18.8∼20°C. From 1967 to 2002, the reservoir was developed by depletion. As a result, the average reservoir pressure has dropped from 5.9Mpa to 1.8 MPa. The serious heterogeneous characteristics and rapid water invasion made the water-cut of wells as high as 76%. Furthermore, the average well production rate declined from the original 8 m3/d to the later 1∼2m3/d., and was staying at this level for a long time. The field was hovering at the economical margin in 2002. In 2003, the operator launched a series of studies and pilot tests to improve the production performance and economic benefits. But there is no proven current recovery technique that can be economically applicable to such viscous oil reservoirs. However, there are huge amount of hydrocarbon accumulation in such reservoirs that can only be exploited with new concepts. Superheated steam huff and puff as a superior technology for the recovery of high water-cut heavy oil reservoirs has been pilot tested in Pre-salt oil reservoir and has found satisfactory development results. This work introduces this new recovery technique of superheated steam huff and puff to effectively develop serious water-invaded heavy-oil reservoirs, and reviews the main practices we have performed, including simulation studies, pilot tests, challenges encountered and solutions, and current effects. Valuable knowledge and experiences have been obtained in terms of superheated steam huff and puff in such reservoirs after many years depletion development, providing reliable operational experience and technical support for Kenkiyak pre-salt reservoir and similar oilfields.
