Frac-pack in Ultra Deep Water: Lessons Learned from a Hundred of Well Succeeded Operations

More than 80% of Brazilian crude oil comes from Campos Basin reservoirs located in deep and ultra deep water depth, producing medium to heavy (high viscous) oil. These reservoirs are clean tertiary age sandstones, unconsolidated, with high to ultrahigh permeability. In this scenario, sand control is mandatory. In order to get low skin completions, one of the best methods is to install frac-packs with high conductivity fractures. These can only be obtained with the use of aggressive techniques applied to very well planned operations. Since the first frac pack job was performed in 1996, many challenges have been overcome, related mainly with 3 areas: The first one is related to the best practices: TCP x HSD perforations, OB or underbalance perforation, pre-job acidizing, clean up flow, real time design, BHTP data collection (from electronic gauges or from live annulus), etc..

The second one relates to unconsolidated high permeability rock fracturing, that means to handling with the leak off in very high permeability, ranging from 300 to 14.000 mD, and the correct use of rock mechanics properties for proper frac pack design. These include minifrac analysis for very low efficiency fracturing fluids, how fracturing fluid efficiency is affected by prior calibration tests, horizontal stress anisotropy for unconsolidated sands, stress contrast for layered sandstones, etc.

And third, due to ultra-high permeability’s, design and pumping questions were imposed: What must be the conductivity of a fracture in formations with such high permeability? Can available commercial simulators be used to design this kind of fracture, considering that they were developed for lower permeability treatments? Is surface pressure data accurate enough to analyze calibration tests? Is the live annulus pressure precise enough? Can it be used for calibration test analysis and to make corrective actions during the main treatment? Can a very aggressive proppant ramp be pumped or even mixed? This presentation brings some answers and more unanswered questions about frac-packs in soft rocks in deep water.

Evento no dia 07 de novembro de 2007 - 12h, na Sede do IBP - Av. Alte. Barroso, 52 - 21º andar - Centro – Rio de Janeiro (RJ). Palestrante: Carlos Alberto Pedroso, da Petrobras - Holds a Chemical Engineer degree from Federal University of Paraná (1986), a Petroleum Engineer degree (1987) and a Master degree in Petroleum Engineering from Campinas University (1996). He has been working with Petrobras as completion engineer since 1987 and as a Technical Advisor in Sand Control and Stimulation, holding patents in this area. He is a guest Professor in Petrobras University.