Carlos Alberto Pedroso

Gravel Packing Deep Water Long Horizontal Wells Under Low Fracture Gradient

Gravel packing very long horizontal wells presents challenges in completion operations. Long horizontal sections of unconsolidated formations, low fracture gradients, and costly rig time are constraints that must be considered in the design and execution of successful gravel-packing completions offshore. Innovative technologies, optimized job designs, and planning are the keys for successful completions.

Triple Frac-Packing in a Ultra-deepwater Subsea Well in Roncador Field, Campos Basin - Maximizing the Production Rate

The key issue to develop the Roncador field, located in ultra deep water offshore Campos Basin, in Brazil, is the maximization of production rate keeping the completion reliability, avoiding premature high workover costs involved in that scenario. Roncador reservoir has a succession of thick turbidite sandstones containing 31 API oil, requiring sand control and water injection to maintain reservoir pressures above saturations. The distance between the pay zones are as short as 12 meters, becoming the first problem to fit the gravel assembly in such a short space. Flexibility in the completion is provided by an internal string with sliding sleeves. When water coning occurs in any zone, the sleeves shall be closed using slick line in a light workover. The paper will describe the main challenges to carry out three stacked frac-packs in a subsea well drilled in water depths above 1800 m, considering the experience acquired from the first three deviated subsea wells, working in dynamic positioned rigs. Special procedures were adopted to prevent failures during the completion, such as: rigid control of fluid cleanness and gel properties, selection and operation of service tools suitable to that environment (heaving, risk of rig drive-off) and careful design for frac-pack based on minifrac data. The drives for equipment selection will be reviewed, including the choice of perforation charges, gravel equipment and sliding sleeves. The good results obtained in those frac-packs, using the Tip Screen Out technique, reducing the skin effect compared to conventional gravel pack, will be presented too.

Case Study of Multiple Hydraulic Fracture Completion in a Subsea Horizontal Well, Campos Basin

Summary This paper provides a case history of the first hydraulic fracture on a subsea horizontal well in the Quissama formation, a low-permeability limestone reservoir in Campos basin, Brazil. The well was drilled in the direction of the expected fracture growth, thus evolving longitudinal fractures along the horizontal section. It is part of a research project to evaluate selective stimulation methods for subsea horizontal wells. Every aspect since the drilling, completion, and evaluation of the well was handled with the end in mind of hydraulically fracturing it in several stages. Hydraulically fracturing a horizontal well has become a more accepted practice in our industry. The procedures used in fracturing vertical wells must be taken into consideration when fracturing a horizontal well, to avoid refracturing work. Near-wellbore (NWB) problems are usually the main reason that fracturing work is not completed. This paper describes hydraulic-fracture treatments with detailed discussion on analysis of calibration tests, fluid-efficiency tests (FETs), and lessons learned. Results of the pumping work will be presented showing theory and how common practices played a key role for a successful application of techniques used. Laboratory tests performed with cores taken from the well itself, such as rock mechanics, proppant embedment, compaction measurements, and basic mineralogy, are presented. Production results will be presented and compared to conventional methods used on other subsea horizontal wells in Campos basin.