Permeability reduction resulting from asphaltene deposition in porous media needs to be accounted for by reservoir simulators. Two questions have to be answered in order to quantify the reduction in permeability. The first question is how much asphaltene is deposited in porous media and the second one is how much permeability reduction is associated with a certain amount of asphaltene deposition. This article focuses on answering the latter by conducting laboratory experiments. Sand packs with known porosity, permeability, and sand grain size distribution were saturated with oil. Heptane was used to flood the oil‐saturated sand packs. After flooding with heptane, each sand pack was divided into ten smaller sand packs and the permeability of each small sand pack as well as the amount of deposited asphaltene in each one of them were measured. A method was developed to quantify the amount of deposited asphaltene within different cross sections of the sand packs. Results have been reported in terms of the mass of asphaltene in milligrams deposited on one gram of sand grain. The formation damage factor for each sand pack segment has been reported as the ratio between the permeability of the segment before extracting asphaltene to its permeability after extracting asphaltene. This ratio varied between 0.4–0.9. Asphaltene deposition varied between 1–20 mg/1 g of sand grain. Comparing the experimental results with the result predicted by one of the current correlations showed that the correlation does not accurately predict permeability reduction.

As consequence of pressure drop in oil reservoirs, production of oil will be difficult and EOR methods are used to improve recovery. In many countries Polyacrylamide is used for polymer flooding in EOR processes, but the problem is that Polyacrylamide is expensive also Acrylamide needs to be handled using best laboratory practices (such as having safe systems of work and wearing appropriate gloves, lab coat etc.) to avoid poisonous exposure since it is a neurotoxin.

The most prominent factor in using UBD is to eliminate or minimize formation damage provided that underbalanced condition maintained 100% of the time during drilling operation. However, during a UBD operation, it is difficult to guarantee that the drilling fluid pressure is always maintained in underbalanced condition. A series of dynamic filtration and return permeability tests have been conducted using reservoir sensitivity core flood apparatus to investigate the permeability alteration due to transition of UBD condition to overbalance one during UBD operation. The results evinced significant permeability reduction when diesel was used as a drilling fluid without any extra additives, due to lack of mud cake and consequently invasion of fine particles existing in the diesel used as drilling fluid for UBD operation into the core samples. Results were plotted in terms of permeability versus diesel volume lost into the formation per square inch of wellbore wall and a linear pattern was found for permeability reduction. So, better plan of UBD operations is necessary for the industry to avoid undesired permeability reductions and it is crucial to develop ways to have an underbalanced condition all the time while drilling and to use filtered diesel or diesel with low solid particle content as a UBD drilling fluid, knowing that usually we do not use loss control materials in UBD drilling fluids. In addition, completion should be planned to be conducted without exposing the formation to overbalanced pressure.

Formation damage due to asphaltene deposition in oil reservoir is an issue for many countries that can have strong effect on oil production during heavy oil recovery, miscible flooding, and even primary recovery. Many tests were performed by researchers to determine the amount of deposition and reduction of permeability but the boundaries in which the asphaltene deposited in oil or at the pore surface are not determined.In this paper, series of tests are performed in order to determine the effect of asphaltene deposition on sandstone rock. Assuming negligible change of viscosity due to various concentrations of asphaltene added, results of laboratory tests performed using pre-separated asphaltene contents from crude oil are showed, to be sure that the first stage (if we divide it into precipitation from liquid phase and deposition on pore surface) of depositing is passed, n-hexane used to flocculate asphaltene particles. To generate reliable data on formation permeability damage due to asphaltene deposition, several dynamic displacement experiments with oil asphaltene content were conducted in various rates and concentrations.These laboratory tests have shown evidence of core damage happening under dynamic flowing conditions. Data were plotted in order to determine the effect of permeability reduction with comparison to reference oil permeability. It shows a significant permeability reduction after flooding. The results have shown that removal and deposition processes occurred simultaneously and trends were similar to previous works where they follow a straight-line pattern except where removal occurs. The previous available models on CMG roughly matched the data.The test results and data can be used in formation damage due to asphaltene deposition models for matching and checking models available in literature and commercial softwares.

The deposition of asphaltene in porous media and their interaction with rock and fluids represent complex phenomena which needs to be investigated under dynamic flowing condition. It could occur by reducing mobility (λ=k/µ) in three probable mechanisms of asphaltene included damage: a) blocking pore throat, b) altering wettability, and c) increasing the reservoir fluid viscosity and can have strong effect on oil production through heavy oil recovery, miscible flooding, and even primary recovery. Many experiments were performed by researchers to determine the amount of deposition and permeability decline but the boundaries in which the asphaltene deposited in oil or at the pore surface was not determined, thus the models introduced have some difficulties using all parameters.In this paper, a mathematical model is developed constructing to simulate rock-fluid interactions describing permeability decline due to asphaltene deposition. The model considers the second stage (if separated into liquid phase precipitation and pore surface deposition) of asphaltene deposition in which n-hexane used to flocculate asphaltene particles in order to determine the effect of deposition on sandstone rock due to changing of pressure, temperature, and composition of reservoir oil. The influences of various injection rates and concentrations are considered carefully.This model simulation and corresponding analytical method is applied using laboratory data gained by performing various dynamic displacement experiments with pre-separated oil asphaltene content resulted a close agreement so it could predict the trend of permeability reduction due to deposition of asphaltene. So the procedure of matching the parameters is described here.This model can be used for analysis of laboratory core tests of formation damage due to flocculated asphaltene particles. Thus, the present study leads to a new insight into the mathematical explanation of flow behavior in porous media.