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.

This paper was prepared for presentation at the 1999 SPE European Formation Damage Conference held in The Hague, The Netherlands, 31 May–1 June 1999.

A multidisciplinary study has been carried out so as to characterize the permeability impairment due to suspended particles during water injection. The approach is based on extensive laboratory experiments reproducing the complete range of parameters met in the industry. Experiments were carried out at both constant flowrate and constant pressure gradient. They reproduce static filtration conditions, i.e. without a flow component tangential to the rock face such as can occur when there are open fractures. The analysis of experimental results has confirmed that injectivity damage can be separated into two successive processes. Internal permeability damage close to the entry face switches to the build-up of an external filter cake after the injection of a critical volume. This is true even when particles are very small as compared to the size of the pore throats. Analytical equations have been developed for each mechanism, as well as for the critical cumulative injection when the external cake starts to form. These equations require at most two parameters. The extensive range of experimental conditions in our laboratory study enables us to propose correlations for the values of these parameters from basic data (velocity, concentration, particle size). Introduction Many oil fields, if not the majority, are produced using water injection which plays the two roles of sweeping oil towards the production wells, and maintaining pressure and therefore productivity at the production well. The quality of water to be injected has a major impact on the economics of waterflooding. Surface water treatment most often involves chlorination, filtering and deoxygenation. It is expensive both in capital costs, particularly topside when offshore, as well as increased operating expenditure. This leads to a strong economic incentive to reduce water quality to the minimum required. On the other hand inadequate water quality can result in dramatic formation damage, failure to meet the water injection target, and sooner or later loss of the oil revenues which were anticipated from waterflooding. Thus water quality is a compromise which needs to be optimized. Optimizing water quality requires a reliable prediction of formation damage as a function of cumulative water injection, for the different water qualities that can result from different treatment facilities, and in particular different filtration criteria. The purpose of this study is to propose simple analytical equations predicting formation damage due to the injection of solid particles, and this should help to optimize the design of water injection facilities. Review of previous models. Formation damage during water injection due to the presence of particles has been the subject of numerous publications, and the recent papers published by Van Velzen and Leerlooijer1, and Pang and Sharma2 present excellent reviews of previous approaches due to Barkman and Davidson3, Eylander4, Rege and Fogler5, as well as Todd et al.6. Van Velzen and Leeriooijer1 carried out a large number of laboratory experiments and interpreted the permeability damage observed in terms of the continuous growth of internal damage. A mathematical description of this process was proposed, making use of Darcy's law, the material balance for the solids in suspension and in the internal filter cake, and a modified Iwasaki7 relationship for deep-bed filtration.

Stand alone screens is a sand control technique that has been widely used in the industry for many years. However, some failures have been experienced, raising some concerns about the validity of design and operating procedures. Contrary to gravel pack for which Saucier criteria is well accepted, design criteria for a sand screen only has always been subject to discussion. As it is a simple and cost effective sand control solution, there is still an incentive to develop more robust design and installation rules.Within Total, a large experience was built in running stand alone screens that allowed optimizing installation practices. In addition, a multi-year laboratory experiments program was run to establish the key parameters in designing stand alone screens. Results of this work are discussed in this paper.First, an experimental work flow was developed and made reliable after evaluating consistence and repeatability of results.Then, a sizing criteria based on the retention of the largest sand grains was confirmed to be pertinent.At last, it was demonstrated the sand size distribution does not have any impact on the sand retention performance of a screen. It cannot be the origin of screen plugging. This work will set new standards in stand alone screen design in Total.

fax 01-972-952-9435. AbstractTo predict correctly injectivity for Produced Water Re-Injection (PWRI), a good description of the formation damage by oil and solid particles have to be introduced in simulators for both fractured and non fractured flows. It is well known that the complex mechanisms of the formation of an external filter cake and of a deep internal damage should be better understood. In a previous published work 1 we attempted to quantify the petro-physical external filter cake properties. In this paper, results from core flood experiments (CFE) aimed to quantify the internal damage are presented. In recent published works, CFE were performed to examine, along rock samples, the deposition profile of only solid particles. The present work focuses on the oil droplets deposition profile. The mechanisms and laws governing the internal damage with oil are different from those concerning solid particles. Like solid particles, oil tends to deposit preferentially at the core entrance but quickly a moving front of oil droplet is generated. According to our experimental results a simple method for modeling the evolution of the internal damaged permeability is presented and finally an attempt is made to extrapolate these results to the well scale for both matrix and fractured flows.