Marginal Oilfields are refered to as those oilfields that are hardly developed efficiently with current technical and ecomonical conditions, characterized as high costs of development and low profit margins. However, under certain economical and technical circumstances, marginal oilfields may be transferred to be conventional ones. Since Petrobras developed the first ever offshore deep reservoir (Lula) by scale in 2006, Brazil has been conducting a progressive campaign targeting hydrocarbons buried under deep water, which contributes to discovery of Lula, Carioca, Jupiter, Buzios, Libra and other giant presalt reservoirs in Santos Basin. CNPC signed a cooperation contract with Petrobras in 2013, taking 10% of the total shares. How to efficiently develop the oilfield has been a challenging issue.

Technologies of smart water injection in Shengli Oilfield have been studied, while the field development and environment (deep water) of Libra Oilfield have been analyzed, in order that the smart water injection technologies may be modified to develop the marginal oilfield more efficiently.

Different from conventional zonal water injection technologies, the remote wireless control water injection technologies take advantages of packers that are connected with each other via preset cables, which achieves downhole testing and water injection simultaneously. Being run via tubing, the water injection string locates a nozzle for each reservoir that is isolated by a packer. All nozzles are connected with packers via the preset cables that work as power lines for the whole string, so that downhole data such as pressures, flows and temperatures are all transferred to the processing computer on the surface. The computer program is used to convert pressure and formation signals into curves that are transferred to Company via WIFI or mobile 2G/3G/4G webs, in order that technicians there may understand and learn about downhole pressures, temperatures, flows and nozzle conditions in real time. They are able to open and close the nozzles totally or partially by giving orders that are transferred as signals via cables. In order to cope with offshore environment of Libra Oilfield in Santos Basin, pre-set cable packers have been modified accordingly, so that highly deviated wells may be developed with the smart water injection technologies.

A field trial deployed in BM-C-33 Block Libra Oilfield shows that the modified smart water injection technologies are feasible for Libra Oilfield, as a novel solution to inject water in highly-deviated and horizontal wells in offshore oilfields.

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