TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractInjectivity decline is a chronicle disaster during produced water re-injection (PWRI); the phenomenon has been widely reported in the literature for North Sea, Gulf of Mexico and Campos Basin fields. The damage happens due to solid and liquid particles in the re-injected water. The injectivity decline prediction is important for planning and design of PWRI, of injected water treatment and of well stimulation procedures. The reliable prediction should be based on mathematical modelling using well injectivity index history and laboratory data.The mathematical models for deep bed filtration of particles and for external filter cake formation have been developed and adjusted to coreflood and well data by numerous authors (Sharma, Khatib, Wennberg et. al.). Here we add modelling of external cake erosion during well closing by the growing cake and filling the well by the erosion particles and develop a comprehensive model.The comprehensive model predicts very peculiar injectivity index (II) curve: initial II increase due to displacement of oil by less viscous water, slow II decline due to deep bed filtration, fast II decrease during external filter cake formation, II stabilization due to cake erosion during the rat hole filling by the eroded particles and further II decrease during well column filling by erosion products.The model is implemented in Excel; the software SPIN Simulates and Predicts the INjectivity.We present in details the history matching for three injectors (field X, Campos Basin, Brazil), showing good agreement between modelling and well data. The obtained values of injectivity damage parameters lay in the same rage intervals as those calculated from laboratory corefloods.
Abstrac tSevere fall of injectivity in porous rock occurs from the practice in offshore fields of injecting sea water containing organic and urineral inclusions . In general, injection of a poor quality water in a well curtails its injectivity . The injectivity loss is assumed to be due to particle retention in the porous rock .A model for porous rock damage due to retention in Jeep filtration during injection of water containing solid particles is formulated. The model contains two empirical functions that affect loss of injectivity -filtration coefficient and damage coefficient versus deposited particle concentration.We show how to solve the inverse problem for determining the first function based on effluent particle concentration measurements in coreflood tests .The second inverse problem is the determination of the formation damage coefficient from the pressure drop history on a core . These two methods allow determining from laboratory tests the information necessary for prediction of well impairment .
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSevere fall of injectivity in porous rock occurs from the practice in offshore fields of injecting sea water containing organic and mineral inclusions. In general, injection of poor quality water in a well curtails its injectivity. The injectivity loss is assumed to be due to particle retention in the porous rock.A model for porous rock damage due to retention in deep filtration during injection of water containing solid particles is formulated. The model contains two empirical functions that affect loss of injectivity -filtration coefficient and damage coefficient versus deposited particle concentration.We show how to solve the inverse problem for determining the first function based on effluent particle concentration measurements in coreflood tests.The second inverse problem is the determination of the formation damage coefficient from the pressure drop history on a core. These two methods allow determining from laboratory tests the information necessary for prediction of well impairment.
10Deep bed filtration of particle suspensions in porous media occurs during water injection into oil reservoirs, drilling fluid 11 invasion into reservoir productive zones, fines migration in oil fields, bacteria, virus or contaminant transport in groundwater, 12 industrial filtering, etc. The basic features of the process are advective and dispersive particle transport and particle capture by the 13 porous medium. 14 Particle transport in porous media is determined by advective flow of carrier water and by hydrodynamic dispersion in micro-15 heterogeneous media. Thus, the particle flux is the sum of advective and dispersive fluxes. Transport of particles in porous media is 16 described by an advection-diffusion equation and by a kinetic equation of particle capture. Conventional models for deep bed 17 filtration take into account hydrodynamic particle dispersion in the mass balance equation but do not consider the effect of 18 dispersive flux on retention kinetics. 19In the present study, a model for deep bed filtration with particle size exclusion taking into account particle hydrodynamic 20 dispersion in both mass balance and retention kinetics equations is proposed. Analytical solutions are obtained for flows in infinite 21 and semi-infinite reservoirs and in finite porous columns. The physical interpretation of the steady-state flow regimes described by 22 the proposed and the traditional models favours the former. 23Comparative matching of experimental data on particle transport in porous columns by the two models is performed for two sets 24 of laboratory data. 29Severe injectivity decline during sea/produced water 30 injection is a serious problem in offshore waterflood 31 projects. The permeability impairment occurs due to 32 capture of particles from injected water by the rock. 33The reliable modelling-based prediction of injectivity 34 decline is important for the injected-water-treatment 35 design, for injected water management (injection of 36 sea-or produced water, their combinations, water fil-37 tering), etc. 38 The formation damage induced by penetration of 39 drilling fluid into a reservoir also occurs due to particle 40 capture by rocks and consequent permeability reduc-41 tion. Other petroleum applications include sand produc-42 tion control, fines migration and deep bed filtration in 43 gravel packs.
Injectivity decline during sea/produced water injection is a wide spread phenomena in offshore and onshore waterflood projects. It happens due to capture of solid and liquid particles from the injected water by the rock resulting in permeability decline and also due to formation of low permeability external filter cake on the wellbore. Both phenomena result in injectivity impairment. The field injectivity decline history is used for characterisation of the formation damage system and for the consequent well behaviour prediction. The injectivity index increases M times during the damage-free displacement of oil by water (M is the water-oil mobility ratio). It affects the well injectivity prediction during poor quality water injection and changes the results of injectivity decline curve interpretation. The combined effect of injectivity impairment by internal and external cakes and of the total oil-water mobility variation can be described by an analytical model. The model contains four injectivity damage parameters: the filtration and formation damage coefficients, the critical porosity ratio and the filter cake permeability. The reliable modelling-based prediction of injectivity decline from a well injectivity index history requires knowledge of the four above-mentioned parameters. In the current paper we develop a method for determination of the four injectivity damage parameters from the well injectivity history. Seventeen well data from eleven different oilfields have been treated, and the values of the four parameters lie in the same intervals as that obtained from laboratory tests. It validates the proposed method for injectivity decline system characterisation and allows recommending this method for prediction of injectivity decline from a well injectivity history. Introduction Drastic decline of injectivity is a wide spread disaster in offshore and onshore waterflooding and during produced water re-injection in oil reservoirs[1,2]. The reason for injectivity decline is the formation of internal and external cakes by solid and liquid particles containing in the injected aqueous suspension. The mathematical models for deep bed filtration of suspended particles with internal cake formation and for development of the external filter cake are well established[3–6]. The models are used for injectivity index decline forecast[4–7]. The reliable prediction of injectivity decline from a well injectivity index history would allow planning of injected water treatment and well stimulation procedures. The reliable prediction should be based on mathematical modelling using parameters, which are to be well known for the specific well/field. The formation damage system is characterised by four parameters: filtration and formation damage coefficients, critical porosity fraction and filter cake permeability[4–6]. Nevertheless, just three constants can be extracted from well injectivity decline curve: the impedance slope during deep bed filtration, the transition time and the impedance slope during external cake formation. The three constants are determined by the four injectivity damage parameters, i.e. the values of three constants form a system of three equations for four unknowns. So, one equation is missing. In order to close the system of equations, one could either assume that the value of critical porosity fraction is known aposteriori[4,6,7], or use the correlation between the critical porosity fraction and the formation damage coefficient as an additional equation[8]. The injectivity index increases M times during the damage-free displacement of oil by water (M is the water-oil mobility ratio). It affects the well injectivity prediction during poor quality water injection and changes the results of injectivity decline curve interpretation[9,10]. Therefore, the varying oil-water mobility should be accounted for in the injectivity damage system characterisation for injectivity decline prediction.
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