Horizontal wells provide increased reservoir contact than conventional vertical wells but present another set of production challenges particularly with respect to imbalanced fluid inflow along the wellbore. This paper will describe the importance of wellbore and reservoir characterization, modelling and practical operational experiences to maximize recovery in a carbonate environment using logging while drilling (LWD) measurements to design reliable and effective completion equipment to manage production. Due to the fractured nature of carbonates and high heterogeneity contrast with the matrix, it is imperative to balance inflow and delay the production of more mobile fluids through the installation of passive inflow control devices (ICD) and swellable packers. Near wellbore steady state and numerical reservoir simulation is particularly important for preliminary design and justification of completion technology. The latter can indicate regions of by-passed oil and areas of high water saturation providing horizontal well infill opportunities. The analysis of real time LWD is essential for well placement but also the characterization of the near wellbore to identify areas of high fracture density and where fluid losses have occurred, to design an appropriate completion tally to maximize production. The availability of adjustable ICDs at the wellsite offers the opportunity to perform this task to fine tune the lower completion design before running in hole. The modelling workflow and operational procedures of optimizing well placement and ICD completion design will be described through carbonate field installations.
Chemical diverter systems, such as relative permeability modifiers (RPMs), can significantly reduce effective permeability, mainly to aqueous-based fluids (e.g., acids), where the fluid enters into the interval being treated. Graded salt is a granular solid used at all temperatures that has a wide particle-size distribution (PSD) for bridging and sealing to provide effective diversion of treating fluids. This combined with an RPM fluid can help divert the entire interval during a matrix-acid stimulation. This paper discusses a review of wells treated, with excellent results, using such a chemical and bridging diversion system (CBDS) in different fields in the southern region of Mexico.
If a formation has zones containing a large number of open, natural fractures, the resulting tendency is for treatment fluids to flow into the zone(s) with the highest effective permeability or the least amount of damage instead of creating a uniform distribution over the entire interval, as is necessary. An important characteristic for a diverter product is creating a temporary skin effect during the injection of the treatment that leaves no permanent damage or that can later be removed or dissolved.
The focus of this study was on gathering more detailed information for the selection of the diverter, treatment design, and operational procedures. Additionally, the learning curve is presented associated with the challenge of stimulating a specific zone within a complex mechanical wellbore and selecting the correct candidate for applying a schedule of mechanical diversions and acid stimulations.
Laboratory study data are included to illustrate how the diverting process physically manifests, which is used to substantiate the field designs. Understanding how chemical diverters interact with the formation rock and fluid is fundamental to selecting the proper product for a specific treatment application.
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