Alexandre Vaz

Well injectivity decline for nonlinear filtration of injected suspension: Semi-analytical model

Injectivity decline due to injection of water with particles is a widespread phenomenon in waterflood projects. It happens due to particle capture by rocks and consequent permeability decline and also due to external cake formation on the sandface. Since offshore production environments become ever more complex, particularly in deep water fields, the risk associated with injectivity impairment due to injection of seawater or re-injection of produced water may increase to the point that production by conventional waterflood may cease to be viable. Therefore, it is becoming increasingly important to predict injectivity evolution under such circumstances. The work develops a semi-analytical model for injectivity impairment during a suspension injection for the case of filtration and formation damage coefficients being linear functions of retained particle concentration. The model exhibits limited retained particle accumulation, while the traditional model with a constant filtration coefficient predicts unlimited growth of retained particle concentration. The developed model also predicts the well index stabilization after the decline period.

Skin Due to Fines Mobilization, Migration, and Straining During Steady-State Oil Production

Abstract Permeability decline during core floods with high rates has been widely reported in the literature. It has often been explained by the lifting, migration, and subsequent plugging of pores by fine particles, which has been observed in numerous core flood tests. The phenomena have been connected to well productivity impairment during fines production that also has been widely observed in oilfields. The authors derive a formula for skin factor based on the modified particle detachment model with maximum retention function. The mobilized fines capture by the rock is assumed to be instant at the large reservoir scale, so skin factor drops at the beginning of production and remains constant. The fines migration induced skin is shown to increase with increase of rate and initial attached fines concentration.

Formation-Damage Evaluation From Nonlinear Skin Growth During Coreflooding

Injectivity decline of oilfield injection wells is a widespread phenomenon during seawater/produced-water injection. The decline may result in significant cost increase of the waterflooding project. Reliable modeling-based prediction of injectivity-index decrease is important for waterflood design as well as for the planning of preventive injected-water treatment. One of the reasons for well injectivity decline is permeability decrease caused by rock plugging by solid/liquid particles suspended in the injected water. The mathematical model for deep-bed filtration contains two empirical functions: the filtration coefficient and the formationdamage coefficient. These empirical coefficients must be determined from laboratory coreflood tests by forcing water with particles to flow through the core samples. A routine laboratory method determines the filtration coefficient from expensive and difficult particle-concentration measurements at the core effluent; then, the formation-damage coefficient is determined from inexpensive and simple pressure-drop measurements. An alternative three-point-pressure method uses pressure data at an intermediate point of the core, supplementing pressure measurements at the core inlet and outlet. The method provides unique and stable values for constant-filtration and formation-damage coefficients. In the current work, we consider a more complex case in which both coefficients are linear functions of retained-particle concentration. In this case, the model is fully determined by four constants. The three-point-pressure method furnishes unique values for the four model parameters. A new semianalytical model for axisymmetric suspension filtration was developed to predict well-injectivity decline from the linear coreflood data with pressure measurements in three core points.

Well Productivity Decline due to Fines Migration and Production: (Analytical model for the regime of strained particles accumulation)

Well index decline has been widely observed for oil, gas and artesian wells producing the reservoir fines. It has often been explained by the lifting, migration and subsequent plugging of pores by fine particles, which have been observed in numerous core flood tests. In this work, the basic equations for the detachment of fine particles, their migration and size exclusion, causing the rock permeability decline, have been derived. The analytical model, developed for the regime of steady state production with gradual accumulation of strained particles, show the linear skin factor growth vs time and vs the amount of produced reservoir fines. Introduction Well productivity decline under fines production is well known phenomenon in low consolidated and high clay contents reservoirs, and also in heavy oil and high rate gas fields (Mungan, N. 1965, Bernard, 1967, Lever and Dawe, 1984, Tiab and Donaldson, 1996, Civan, 2007). It is explained by detachment of the attached particles and clay fines by the drag and lifting forces, exerting the fine particles from the moving fluid; the mobilised fines strain thin pores causing the permeability decline. The reliable prediction of productivity index decline is based on the mathematical modelling. Kinetics of particle capture by the rock from the flowing suspension is described by the filtration equation (Herzig et al., 1970)

AVALIAÇÃO DO POTENCIAL USO DE BIOGLICERINA COMO BASE PARA FORMULAÇÃO DE FLUIDOS DE PERFURAÇÃO AQUOSOS PARA POÇOS DE PETRÓLEO E GÁS

Cleysson C. Corrêaa, Georgiana F. da Cruza,*, Alexandre S. L. Vaz Jra, Bianca de S. A. Araújoa, Alexsandro A. da Silvab, Rafael A. Rodriguesb , Rosana F. T. Lombac e Alex T. de A. Waldmannc Laboraório de Engenharia e Exploração de Petróleo, Universidade Estadual do Norte Fluminense Darcy Ribeiro, 27.925-535 Macaé – RJ, Brasil Central Analítica Fernanda Coutinho, Instituto de Química, Universidade do Estado do Rio de Janeiro, 20550-900 Rio de Janeiro – RJ, Brasil Centro de Pesquisas e Desenvolvimento Leopoldo Américo Miguez de Mello, Cidade Universitária, 21941-915 Rio de Janeiro – RJ, Brasil

Fines Migration in Aquifers and Oilfields: Laboratory and Mathematical Modelling

Migration of natural reservoir fines is one of the main causes of formation damage in oil and gas fields. Yet, fines migration can be employed for enhancing reservoir sweep and water production control. Permeability decline due to fine particles’ detachment from reservoir rocks, mobilisation, migration and straining has been widely reported in the petroleum industry since the 1960s and is being researched worldwide. The topic of colloidal-suspension flows with particle detachment is also of wide interest in environmental, chemical and civil engineering. The current work begins with a detailed introduction on laboratory and mathematical modelling of fines migration, along with new mathematical models and experimental results. Each of the next three sections explores a particular cause of fines mobilisation, migration and straining. Section 2 covers high flow velocity that causes particle detachment accompanied by consequent permeability decline. Section 3 covers low-salinity water injection, where the decreased electrostatic attraction leads to particle mobilisation. Section 4 covers the effect of high temperature on production rate and low-salinity water injection in geothermal reservoirs. We attribute the long permeability stabilisation period during coreflooding with fines migration, to slow fines rolling and sliding and to diffusive delay in particle mobilisation. We derive the analytical models for both phenomena. Laboratory fines-migration coreflood tests are carried out, with the measurement of breakthrough fines concentration and pressure drop across the whole core and the core’s section. Treatment of the experimental data and analysis of the tuned coefficients show that the slow-particle model contains fewer coefficients and exhibits more typical strained concentration dependencies of the tuned parameters than does the delay-release model.

A New Phenomenon of Slow Fines Migration in Oil and Gas Fields (Laboratory and Mathematical Modelling)

Fines migration causes significant permeability damage, due to mobilisation of particles at increased velocities, their migration in pores followed by straining at pore throats and attachment to pore walls. Numerous coreflooding tests with piecewise increasing rates are conducted. There are two main features of these tests: the first is long-term injection, which allows calculating permeability stabilisation time; the second is pressure measurement at intermediate points, allowing for evaluating the permeability profile along the core. The impedance data obtained from experiments are matched with the results from analytical model. It shows that the mobilised particles move with velocity much smaller than the carrier fluid, yielding long time for permeability stabilisation. It contradicts the classical filtration theory, which indicates the fines are transported with the carrier fluid velocity.

Modelling of Slow Fines Migration and Formation Damage During Rate Alteration

Fines migration involving particle detachment in reservoirs often leads to severe permeability damage. It is the consequence of straining of the detached fines in relatively narrower pore throats. Many laboratory coreflood tests indicate that the time of permeability stabilisation can reach hundreds or thousands of pore volumes injected. However, the classical filtration theory assumes that the mobilised fines are transported by the bulk of the carrier fluid, thus the permeability stabilises after one pore volume injected. The current paper attributes the stabilisation delay to the slow drift of the released fines close to the rock surface. We propose the system of flow equations for fines migration in porous media taking into account the velocity of particles lower than that of the fluid. An analytical model for one-dimensional flow with particle mobilisation and straining during piecewise increasing flow rate is obtained. The laboratory data are in good agreement with the results of mathematical modelling. The effective particle speed is 500-1000 times lower than the water velocity.

Prediction of Productivity Decline in Oil and Gas Wells Due to Fines Migration: Laboratory and Mathematical Modelling

Suspension-colloidal transport in porous media with the particle detachment usually exhibits a significant permeability decline. It occurs due to mobilisation and migration of detached colloidal or suspended fines with their straining in thin pores of the rock. Numerous laboratory coreflood tests show that the time for permeability stabilisation counts for hundreds of injected pore volumes, while the classical filtration theory assumes the released fines transport by the bulk of the carrier fluid yielding one pore volume injection to stabilise the permeability. In the current paper, the stabilisation delay effect is explained by slow drift of the mobilised fines near to pore walls. The basic flow equations for a single-phase particle transport in porous media with velocity lower than the carrier fluid velocity are proposed, and the analytical model for one dimensional flow with particle release and straining under the piece wise increasing velocity is derived. The laboratory data are in a good agreement with the results of mathematical modelling. The analytical model for well inflow performance is developed. It successfully matches several field cases.