Improved Lost Circulation Treatment Design and Testing Techniques Minimize Formation Damage

Abstract

Most subterranean rocks contain natural fractures. Fluid loss severity in reservoir sections increases with increasing width of the fractures. Apart from the economics of lost drilling fluids, preventing formation damage in the reservoir section is of paramount importance. The application of non-damaging lost circulation material (LCM) has been the traditional solution to control losses in these scenarios. The performance of such LCM mixtures is usually determined with a Particle Plugging Apparatus (PPA), using aloxide discs for evaluating fluid loss. These discs more closely emulate a permeable sandstone, with varying pore throat sizes, than a natural fracture. The formation of an impermeable plug which can sustain higher wellbore pressure is desirable when treating a fracture, but in a producing formation the plug is removed by the produced fluid or by a remedial treatment.To better emulate both natural and induced fracture geometry, slotted discs of constant width were introduced; however these slots represent only the face of the fracture where LCM forms the bridge. The bridge may become eroded due to shear stress of the drilling fluid, leading to reestablishment of lost circulation. To remove these limitations, a new tapered slot was designed in which the fracture opening size varies from its face to its endpoint over a certain length, more closely resembling a fracture.Different combinations of ground marble (acid-soluble) were tested using the tapered slot. Many times it was observed that although the slot was completely filled with LCM, there was continued fluid loss. Considering this, components of high fluid loss pills for such application need to be redesigned. Cellulosic and polylactide (PLA) fibres (5-15% V/V of LCM) were used in combination with particulates resulting in significant improvement in fluid loss control. Other mechanical properties of particulate material were also studied and their importance in controlling lost circulation control established. This paper reviews the application of this testing equipment and methodology with non-damaging fibers for lost circulation control to minimize formation damage in reservoir sections.

Alternative Lost Circulation Material for Depleted Reservoirs

“…(Miller et al 2013;Savari et al 2011;Savari et al 2013; Cement Cement is one of the most common LCM. This engineered approach is based in formulating specific LCM mixtures containing an optimized particle size distribution, generally based in a multimodal PSD design for the suite of material types.…”

Reservoir Friendly Rigid Setting Fluid Arrests Lost Circulation While Minimizing Reservoir Damage

“…Minimal or zero fluid loss is always desirable for minimal reservoir damage and optimized production. Savari et al (2011) discuss the two major sources of formation damage, one being the invasion of filtrate (or fluid) and solids during conventional overbalanced drilling and workover operations and the other resulting from the presence of highpermeability fractures in a formation, such as large naturally occurring fractures or an extensive interconnected vugular porosity system. The latter represents a significant challenge for overbalanced drilling operations with respect to rapid and deep invasion and significant permeability impairment.…”

“…This has led both the service providers and operators to examine unconventional LCMs that might be capable of working in severe lost circulation situations. Earlier works (Kumar et al 2010Miller et al 2013;Savari et al 2011Savari et al , 2013a) present the novel concepts in terms of examining different properties of LCMs and improvised methods and tools for testing LCMs, and they also discuss some unconventional LCM combinations. This paper also discusses a novel or unconventional LCM (chemical sealant) that has the potential to arrest or mitigate severe-to-total fluid losses in production zones.…”

Nanoplugging Performance of Hyperbranched Polyamine as Nanoplugging Agent in Oil‐Based Drilling Fluid

“…Journal of Nanomaterials Pressure conditions and plugging performance of the fiber and solid particles for fracture were evaluated [26,27]. The groove diameter is 1000∼2500 m and the width of another metal cutting board is tens of microns.…”