Most of Brazilian oil and gas reserves are located in offshore deep waters. In this scenario, high well productivity is essential. Artificial lift will certainly play an important role in the exploitation of those deep water fields.
This paper describes the most important artificial lift methods, their main characteristics and application niches. It also shows what Petrobras is currently doing in order to make them available for subsea use.
The following methods are analysed:
gas lift;
electrical submersible pump;
hydraulic jet pump;
progressing cavity pump;
multiphase pump;
subsea separation system.
Petrobras is the world leader in subsea completion. For subsea application only gas lift has been widely used as artificial lift method, due to its intrinsic similarity with onshore's gas lift method. This similarity comes from the fact that it is driven by a power fluid using roughly the same components for both onshore and subsea application. For this reason, gas lift is today seen as the subsea conventional artificial lift method. Sometimes, gas lift may not be the best method to fit specific field's requirements. This happens, for instance, when there are long distances between well heads and platforms, and the gas injected, even though helping the flow in the vertical sections (well and riser), increases pressure drops in the horizontal section (flow line). Additionally, this method demands compressors and an increase of gas facilities to handle the extra recycling gas, with consequent drawbacks on platform weight and area requirements, which have a high impact on offshore installations costs. Of course, there are other limitations for the gas lift method, but this will be addressed later.
As a major oil company, with large offshore hydrocarbon reserves and more than 60% of nowadays' total production coming from offshore wells, Pepobras is currently feeling the need to adapt some artificial lift techniques, in order to make them available for subsea use as an alternative to the conventional gas lift method. Petrobras believes that each of these options may find some fields with adequate set of characteristics that make them the proper choice for their exploitation.
This paper describes the major characteristics of each method currently under development for offshore use (focusing on subsea applications), the expected characteristics of theirs application niche (advantages and disadvantages), the probable major problems for their extension to subsea use and their current development stage at Petrobras.
In this item it will be discussed the main characteristics of each method, as well as the difficulties to adapt them to subsea use. What Petrobras is currently doing and planning to do for each method will also be discussed.
