Precipitation and deposition of heavy organic materials such as asphaltene inside reservoirs, processing and transportation facilities is a major concern in the oil industry. Asphaltene precipitation is one the most common problem in many reservoirs and unfortunately may lead to many safety operational issues that in end affect's oil recovery which assumes to be a major economical loss. The precipitation and deposition of asphaltene in porous media and their interactions with rock and fluids is a complex phenomenon which begs to be investigated under reservoir conditions. As yet, there have been many studies conducted on asphaltene precipitation but majority of them focused on determining precipitation onset point. It is believed, the first step in attempting to find an engineering solution to this deposition problem is to identify the conditions at which asphaltene precipitation takes place initially and conditions after that influences deposition. This paper presents an assessment of aspects that influences asphaltene precipitation and deposition. This research, attempts to understand the mechanism of asphaltene precipitation and deposition, parameters affecting the precipitation and deposition process, the effect of asphaltene precipitation and deposition on oil reservoir characteristics and performance. In addition, the research involves examining the existing thermodynamic models of asphaltene precipitation and deposition in porous media, reversibility of asphaltene precipitation and deposition, asphaltene deposition removal methods, and modelling and simulation of asphaltene by conventional simulators. Since this study is a comprehensive summary of the mentioned topics and contains all the essential information of asphaltene and its precipitation process, it therefore can be used as a reference for further exploration of this specialized field.The probability of asphaltene precipitation and deposition occurring during any EOR techniques and its effects on reservoir performance should be anticipated at earlier stages of any development project. Also it is believed that through a more comprehensive understanding of the mechanisms that lead to deposition in the first place; asphaltenes deposition if cannot be prevented fully may at least be controlled and managed.

Mature oil wells with high water cut suffer from solids deposition with an agglomeration of species like asphaltenes, wax, resin, metal naphthenates, inorganic scale and formation fines etc. Such solids generally accumulate around the well bore, in the production tubing and surface facilities. These deposits can also change the formation wettability towards oil wet. Solid deposition and wettability change create additional resistance to flow in producing wells leading to decline in rate of oil production. Generally in such cases the production decline can be very steep.Analysis of some deposit samples from such producing wells in Malaysia shows the presence of macro and micro-crystalline waxes, asphaltenes, resins, metal naphthenates, inorganic scale, sand, silt, clay etc. in varying concentrations. The presence of naphthenate deposits is a new problem in many oil wells. The deposition of naphthenates along with other organic and inorganic components create skin and a restriction to flow. This complex gamut of such deposits, especially naphthenates does not dissolve/ disperse completely with solvent followed by conventional acid treatment. This often results in acid induced sludges. Use of solvents, acid blends and other composite fluids is reported to remediate such problems with varying degree of success.To address the deposit problems induced by naphthenates, an effective micro-emulsion consisting of solvents, surfactants, and inhibited acid etc. has been developed to effectively remove organics. The objective of such treatment is to provide dissolution/dispersion of organics that leads to deeper penetration into near wellbore with no sludge formation. This paper presents laboratory and field data on a treated well from Sarawak which showed significant enhancement in oil production. The well was completed with a gravel screen and exhibited very low productivity from its initial production due to combined completion skin and formation damage. Significant increase of the production rate (from average of 50 bopd to 900 bopd) was observed after the treatment.

Organic deposition predominantly in the near well bore and in production tubing can create serious oilfield problems such as flow restrictions, near wellbore damage, efficiency of crude processing units and etc. As the reservoir depleted over the time, the solid deposition can lead to a steep decline in productivity of wells. The deposition of organic solids is one of many flow assurance problems faced by operators in Malaysia. It has been observed that, after years of production, many fields in Malaysia are suffering from organic solid deposition problem. This phenomenon is predominantly caused by changes in temperature, pressure and composition/morphology of the crude oil over time. To perform organic deposit removal treatment and prevention in the well, the nature of the solid should be characterized. If the deposit sample is organic mainly, it is important to quantify the various organic fractions of the solid sample collected from the production facilities. This paper explains how SARA analysis was modified to detect not only Macro-crystalline waxes (Saturates), asphaltene, aromatics and resins but also micro-crystalline wax and naphthenates. The content of each of above component will affect the method of treatment and the chemical formulation to treat the well. By knowing the composition of the solid sample along with Crude’s Colloidal instability index (CII), Pour point and Wax Appearance Temperature (WAT), a customized chemical formulation can be designed. Lab studies were performed on solid samples collected from several wells to detect the flow assurance related issues prior to design of chemical formulation. With the analysis of the production data, history matching, and etc, a customized chemical formulation was developed to treat the wells. The proposed chemical formulation consists of 2 specially designed pills which would be simultaneously injected to the wellbore, which generates heat and ester once comingles. The heat melts the deposits while the ester disperses the melted solid. The initial studies of the treatment showed promising results; moreover the field implementation was very successful and proven significant increase in production rate. This novel system that combines both thermal and physical energy, evidenced to work effectively for wide range of organic compositions. Implementation of this system made it possible to restart the production from those wells which were idle due to extensive organic deposits. This technique was also often used to rejuvenate the old wells with low production rate. This paper discusses the diagnostic process and successful implementation of the proposed treatment in several oil wells in Malaysia.

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