A Simulator For Produced Water Reinjection in Thermally Fractured Wells

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe objective of the analytical simulator presented here is to predict the opposite and complex effects induced by the injected produced water temperature and formation damage on thermally fractured wells. The deposition of solid particles and oil droplets in a fracture and its effect on the Injectivity Index evolution of an injector is then simulated. The principle is to inject cooled waters like sea water for example during a certain period of time to enable the well to develop a thermal fracture. When the fracture is well established, the re-injection of hot produced waters starts. The model takes into account the effect of this new water temperature on the viscous flow and on the fracture shrinkage and closure. In the same time oil droplets and solid particles contained in produced water cause the damage of the reservoir. This tends to open and propagate the fracture under bottom pressure increase. In the simulator, the internal formation damage and the external filter cake deposition in the fracture occur simultaneously. Two internal formation damage deposition models are taken into account. In a first model the internal damage is supposed to be linear and occurring from the fracture faces to the reservoir. In a second model, despite the growth of the fracture, the internal damage is supposed to be radial and occurring from the wall of the well to the reservoir. Also, two exeternal filter cake deposition models are considered: the filter cake deposits only at the fracture tip or on fracture faces. Theoretical field cases were considered in the simulations. The different internal formation damage and filter cake models were combined together to reproduce the injectivity index evolution observed on real fileds. The example presented are chosen to show that, contrarily to common thinkings, the II evolution can be dominated, in certain circumstances, by the internal damage rather then by the external filter cake deposition. With the present choice of data, the II evolution which matches better the commonly observed field reponses is obtained when the internal damage occurs in radial flow whatever the model deposition of the external filter cake is.

Water Quality and Well Injectivity: Do Residual Oil-in-Water Emulsions Matter?

“…With PWRI, sustaining a long-term injection rate is likely to require fracturing (Zhang et al 1993;Detienne et al 2005; Van den Hoek et al 2008). Matrix injection results in a continuous well-injectivity decline even in soft formations (Detienne et al 2005;Abou-Sayed et al 2007).…”

“…Matrix injection results in a continuous well-injectivity decline even in soft formations (Detienne et al 2005;Abou-Sayed et al 2007). Actually, recent field evidence indicates that most water-injection wells are likely to be fractured (Abou-Sayed et al 2005;Abou-Sayed et al 2007; Van den Hoek et al 2008) and that regular well acidizing is required to maintain injectivity even with clean water (Van den Hoek et al 2008).…”

“…Actually, recent field evidence indicates that most water-injection wells are likely to be fractured (Abou-Sayed et al 2005;Abou-Sayed et al 2007; Van den Hoek et al 2008) and that regular well acidizing is required to maintain injectivity even with clean water (Van den Hoek et al 2008). Thus, injectivity in hard formations is increasingly viewed as being dictated by a dynamic coupling between fracture growth and plugging (Detienne et al 2005). This injection scheme raises additional challenges related to the issues of fracture growth and containment with the risks of early water breakthrough and outof-target injection.…”

Optimised Completion of a Produced Water Re-injection Infill Well

“…Fracturing of seawater injection wells has proven to give sustained high rates over long life, with fracture growth assisted by cold injection temperatures, typically referred to as thermal fracturing 3,4 . However, studies 5,6 have suggested that produced water injectors are more prone to fracture damage and warmer injection means they do not achieve as much benefit from thermal fracturing. Attempts have been made on ETAP, with limited success, to improve PWRI injection rates using short term seawater injection.…”

Internal Formation Damage Properties and Oil-Deposition Profile within Reservoirs During PWRI Operations

“…A new method was recently proposed 6 to quantify parameters λ and β from laboratory pressure measurements using the called 3 point pressure method. Other models 7,8 dedicated to simulate produced water re-injection under fracturing conditions, the depth of the internal damage is simply calculated from the injected volume of oil assuming an oil saturation and a fixed damaged permeability in the invaded zone. For other works 9 the concept of Barkman and Davidson is still used to simulate produced water injectivity decline.…”