The paper presents an overview of the evolution of Petrobras open hole gravel packing operational practices after the 200th well has been successfully completed with this technique in Campos Basin (CB): a milestone in the history of Petrobras completion practices in deep and ultra-deepwaters.
The paper also presents a comprehensive description of the main steps taken to improve our horizontal open-hole gravel packing (HOHGP) practices towards a best-in-class status in unconsolidated oil-bearing turbidites. Since the first HOHGP job done in 1988 we had to move progressively from shallow to ultra-deepwater completion scenarios. Along this path a series of innovations has been incorporated to our sand face completion practices due to the ever-growing-complexity of the wells geometry, longer intervals to be completed, heavier oil reserves to be developed, rock mechanics restraints (ever-lowering fracture gradients) and the necessity of damage-free-, high-performance-wells to cope with the skyrocketing capital expenditures which is a general rule for offshore ultra-deepwaters nowadays.
Petrobras strategy conceived to continuously enhance its HOHGP completion efficiency index encompasses, the following interrelated subjects: -a comprehensive long-term plan to deal with the problem, -a multi-disciplinary team-work approach, -a strong cooperation with gravel packing tools & screens suppliers, -improvement of operational procedures and guidelines against which to measure well performance and -research & investment in cutting-edge technologies.
Discussions on the challenges envisioned for HOHGP operations in ultra-deepwaters in the years to come are also presented.
The most prolific reservoirs in CB are the Upper Cretaceous and Tertiary turbidites. These high-permeability (circa 1000 – 8000 mD), stacked and amalgamated reservoirs are spread over in shallow, deep- and ultra-deepwaters within the Basin. Figure 1. Dictated by the depositional model associated to turbidites, the sand uniformity of these poorly- or un-consolidated sand lenses vary quite a bit. The presence of reactive shale streaks is recurrent in some of these turbidites.
As a trend in many other offshore basins in the world, the first oil discoveries (early in the 1980´s) in turbidites were located in shallow waters of CB. These good exploratory results have propelled us to move progressively from shallow to ultra-deepwaters scenarios. However, since the pioneer oil discoveries we have realized that a sand management strategy was necessary to achieve the desirable levels of production.
In fact, sand control is an umbrella term comprising different approaches to dealing with sand production problems. Different sand control methods are known: frac-pack, chemical consolidation of sand grains, use of screens: sintered mesh, conventional, expandable (ESS); use of slotted liners, gravel packing, inter alia.
Petrobras philosophy is one of zero tolerance concerning sand production in offshore fields lest the governing parameters for sand production are not well established for the vast majority of actual field situations and they may change along the life-span of the wells. Should there be the slightest chance of sand production, a sand control method is installed in our wells. In essence, this preventive approach to sand exclusion stems from the following facts: wellbore integrity concerns, prohibitively high well intervention costs, the need to maximize production rates, to achieve a maximum completion efficiency index, safety concerns, payback economics, and incapability of sand-dealing in top-side equipments. In fact, our offshore production facilities have not been designed to process sand-bearing crude oils.