Paulo Dore Fernandes

A finite element model for three dimensional hydraulic fracturing

This paper is devoted to the development of a model for the numerical simulation of hydraulic fracturing processes with 3d fracture propagation. It takes into account the effects of fluid flow inside the fracture, fluid leak-off through fracture walls and elastic response of the surrounding porous media. Finite element techniques are adopted for the discretization of the conservation law of fluid flow and the singular integral equation relating the traction and the fracture opening. The discrete model for the singular integral equation is implemented using a stencil matrix structure allowing an efficient implementation of the fluid-structure interaction problem. Newtons method combined with GMRES linear solver are used to solve the resulting nonlinear set of equations. An algorithm for fracture propagation is proposed which is based on the balance of the amount of fluid transported to a certain point with the amount of fluid that could be lost by leak-off. To illustrate the feasibility of the model, we present simulation results for typical operational parameters.

Successful Pinpoint Placement of Multiple Fractures in Highly Deviated Wells in Deepwater Offshore Brazil Fields

The application of hydrajet technique to stimulate highlydeviated and horizontal wells has become a successful method to improve well productivity for different field conditions in the world. In the past 2 years, an operator company has successfully implemented a relatively new hydrajet stimulation technique in shallow waters off Brazil. In deepwater locations, additional problems had to be overcome, which proved achievable using this new technology. This paper discusses a reservoir-based methodology to determine the optimum number of transversal fractures for a horizontal deepwater well. The method starts with the review of geology and stratigraphic aspects of the field to better understand the relationship between fracture orientation, geological faults, and regional tectonic effects. With this preliminary characterization, well-log interpretation of the pilot well and horizontal wellbore is performed to identify porosity and permeability index of the carbonate formation being drilled. A study using well testing and nodal analysis is conducted to verify reservoir properties based on real production data. Next, a numerical simulator is used to obtain a production forecast varying the number of transverse fractures intersecting the well. Finally an economic evaluation of net present value vs. number of fractures is performed to determine the optimum number of transversal fractures. Production results are then evaluated and compared to the other stimulation attempts in offshore horizontal completions in the area.

First Applications of a Multiple Fracturing Method in Noncemented Horizontal Offshore Wells

This paper presents the first offshore applications, both in platform and subsea wells, of a multiple fracture creation process in openhole horizontal wells, previously applied in onshore scenarios. The applications had to overcome many challenges typical of workovers on mature field offshore wells. The paper covers detailed workover planning, multiple fracturing designs, operations data, and the stimulation results. The campaign comprised three horizontal slotted liner wells offshore Brazil as part of a research project to evaluate selective stimulation methods for horizontal wells. It was proved that the method can be successfully applied in platform and subsea wells (a first). The economic results were very attractive, making the method an alternative for hundreds of noncemented offshore horizontal wells.

First Implementation of HydraJet Fracture Acidizing in Deepwater Offshore Brazil Fields

The placement of multiple fractures in horizontal, deviated wells is usually more difficult than placement in vertical wells. When completed with uncemented preperforated liners, such treatments become much more difficult and often are ineffective using conventional stimulation methods. When found in offshore locations, these wells present even more problems. Recently, in the shallow waters offshore Brazil, a relatively new hydrajetting technology was used with great success. However, additional complications arose when hydrajet fracturing was elected to stimulate a subsea well. This process requires dual high-pressure connections to the wellbore, including placement of a tubing string inside the full length of the well. Maintaining the hydrajet tool in position during each fracturing stage was a big issue in a floating rig. The need to pull tubing between stages of the stimulation process also poses a challenge. Because this operation occurred in a subsea well, it was the first such application ever attempted worldwide. Extremely detailed planning was essential to the ultimate success of the operation. This paper discusses the rigorous planning involved in implementing multistage hydrajet fracture acidizing in a subsea well offshore Brazil. During the operation, all challenges, mechanical or otherwise, were meticulously scrutinized, including the proper operation of the stimulation vessel and riser motion. This paper also presents posttreatment production results evaluated and compared to other stimulation attempts in offshore horizontal completions in the area.

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.