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SPE Members Abstract Wettability is an important factor in a number of petroleum production processes. Asphaltene deposition can have a strong role production processes. Asphaltene deposition can have a strong role in wettability reversal. Among many factors, the high molecular with, polar fraction of crude oils, including the asphaltenes, are considered to be the primary wettability altering agents. Understanding the role of asphaltene in wettability of reservoir fluids on solid surfaces and its reversal will help us plan for more efficient oil recovery processes. It will also establish the role of asphaltene deposition in the production operation of asphaltic crudes including heavy petroleum crudes. In this paper the groundwork for the study of the complex role of asphaltene and its deposition in altering the wettability of reservoir fluids on solid surfaces is presented. A number of experimental observations in support of the strong role of asphaltene in altering the interfacial tensions and wettability is reported. A new molecular theory for prediction of wettability and its reversal is also prediction of wettability and its reversal is also introduced. Introduction and Background It is well recognized that the presence of asphaltene in a crude oil can add significantly to the problems in a petroleum production field. Properties problems in a petroleum production field. Properties of the asphaltene containing residue of an oil are found not to be consistent with the properties of the lighter oil fractions. The compounds which constitute complex petroleum crudes are mutually soluble so long as a certain ratio of each kind of molecule is maintained in the oil mixture; They are the ratio of polar to nonpolar molecules and the ratio of high to polar to nonpolar molecules and the ratio of high to low molecular weight molecules in the mixture. The necessary mathematical models for the prediction of the onsets and amounts of deposition of asphaltene due to changes in flow conditions, temperature, pressure, and concentrations is already formulated pressure, and concentrations is already formulated The principles of thermodynamics of multicomponent mixtures and phase equilibria, the theory of continuous mixtures, the statistical theory of polymer solution, the concept of streaming potential, and the theory of FRACTAL aggregation kinetics are utilized to develop these models. Asphaltene deposition. is considered to be a major cause of wettability reversal inside an oil reservoir. Wettability is defined as "the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids. Wettability has been recognized as an important factor in a number of oil-recovery-related processes such as waterflood behavior, capillary pressure, and relative permeability. According to the literature the exact permeability. According to the literature the exact mechanism of wettability is not satisfactorily understood. Furthermore, the determination of insitu wettability and application of laboratory results to field conditions are known to be unreliable. It is also known that wetting states of reservoir rocks are inherently difficult to ascertain. Whether the majority of reservoirs are water wet, oil wet, or of intermediate wettability seems still very much a matter of debate and research. P. 799
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.70)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Precipitates (paraffin, asphaltenes, etc.) (1.00)
Asphaltene Management Leading to Significant Reduction of Production Deferment and Operation Maintenance in One of the Sour Fields in Southern Oman
Narwal, Tushar (Petroleum Development Oman PDO) | Alias, Zaal (Petroleum Development Oman PDO) | Kumar, Kamlesh (Petroleum Development Oman PDO) | Abri, Zahir (Petroleum Development Oman PDO) | Dickson, Sara-Jane (Petroleum Development Oman PDO) | Hadhrami, Abdullah (Petroleum Development Oman PDO)
Abstract In Southern Oman, PDO is producing from several critically sour fields (1-10% H2S). Initial flow assurance studies from these fields based on available data at the time did not predict asphaltene plugging issues in depletion mode for most of the fields. However, over the period, wells from one particular field (Field SA3) started experiencing asphaltene deposition in the wellbore, which initially affected only surveillance activities but later led to significant production deferment and posed operational challenges. This paper discusses the asphaltene management strategy developed by the team to tackle asphaltene problem in a systematic manner by improving the current asphaltene detection and cleanout techniques, which led to to reduction in unscheduled deferment by ~50% and the intervention costs by ~20-25%. This work also describes the potential asphaltene risks during gas injection based on an asphaltene study performed on downhole samples.
- North America > United States > Texas (0.68)
- Asia > Middle East > Oman (0.63)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.73)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Management > Asset and Portfolio Management (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Precipitates (paraffin, asphaltenes, etc.) (1.00)
Abstract Successful acid stimulation programs are achieved when more near well-bore damage is removed than is induced by the acid treating fluid. Acid induced asphaltene sludging is becoming an increasing cause of oil well stimulation treatment failure. laboratory tests on 231 crude oils from 17 formations in the U.S. and Canada, have been tested for sludge sensitivity. Numerous chemical processes involved in an acid system contribute to the effect of acid on sludge potential. Surface tension has been used in the past as a guideline for predicting the sludge potential of a chemical system. However, surface tension, in and of itself, is not a factor in acid induced sludge. In addition, this data indicates that as oilfields mature and are placed on secondary and tertiary recovery, sludge sensitivity increases. As a result of this data, a crude oil classification system is presented based on API gravity and asphaltene content. By presented based on API gravity and asphaltene content. By classifying the crude oil, conclusions can be reached regarding sludging potential. This study addresses many such chemical options which include acid strength, acid type, solvent preflush, iron control and additive compatibility. The oxidation potential of iron contaminated acid is also clarified. Introduction An extensive study was conducted by Gidley in 1985 concluding that acid stimulation results on oil wells appear to be site specific and, therefore, appear to be more influenced by the specific nature of reservoir fluid. The fluid interaction between acid and crude oil can produce two major damage mechanisms which affect the success of acid stimulation of oil wells. These mechanisms include the formation of rigid film emulsions and the precipitation of acid induced asphaltene sludgs. While the primary focus of this paper is asphaltene sludging, rigid film emulsions are also discussed. A laboratory study of 231 crudes from 17 different formations in Canada, Texas, Alaska, California, offshore Louisiana and Mississippi was conducted (see Table 1). This study indicates that the sludge sensitivity of a crude can be statistically classified based on commonly available chemical and physical data. In addition, this study shows that commonly utilized acid systems must be adjusted in order to reduce nudging. Lowering acid strength, substituting organic acid, utilizing a solvent tireflush, controlling iron and optimizing the use of additive packages were found to reduce this potential formation damage. Scope of Statistical Study A review of the literature indicates that extensive work has been done on acid induced asphaltene sludging. However, previous studies focused on either specific crudes in limited previous studies focused on either specific crudes in limited geographic areas or on a narrow aspect of chemical effects on sludging. This study encompassed 231 crude samples from the 17 predominant formations in North America known for sludging. The authors have attempted to evaluate the effects of the entire chemical process. It is hoped that future designers of acid treatments can gain insight into a variety of chemical options which will:contribute to the achievement of stimulation objectives and minimize the occurrence of acid induced sludge. Occurrence of Asphaltene Sludge Crude oils are typically categorized as either paraffinic or asphaltenic depending on the nature of the predominant heavy species. Asphaltenes are contained in crude oils in the form of a colloidal dispersion. Amorphous in structure, the asphaltene micelle consists of high molecular weight compounds surrounded and peptized by lower weight neutral resins and aromatic hydrocarbons. The micelle consists of sheets of polycyclic rings containing 6-14 rings per sheet. These sheets polycyclic rings containing 6-14 rings per sheet. These sheets are stacked 5 deep to form the asphaltene particle. The particle has a diameter of 30 to 65 angstroms and a molecular weight ranging from 1,000 to 50,000. Asphaltene sludge which occurs when crude oil contacts acid, can be differentiated from naturally occurring asphaltene deposits. P. 99
- North America > United States > California (0.35)
- North America > United States > Alaska (0.35)
- North America > United States > Louisiana (0.34)
- (2 more...)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Abstract Enhanced-oil-recovery techniques by gas injection in shale reservoirs have been introduced and investigated. Laboratory and simulation works have shown good results for enhanced shale oil recovery, but one problem with gas injection is asphaltene precipitation and deposition. Damage due to asphaltene precipitation and deposition in conventional reservoirs has been reported in the literature. In shale reservoirs, pore and throat sizes are much smaller than in conventional reservoirs. Thus, large asphaltene aggregates may cause more serious problems in shale reservoirs. This experimental study used a nanofiltration technique to investigate the size of asphaltene aggregates precipitated during CO2 and CH4 injection in a shale oil sample. Nano membranes of 200nm, 100nm and 30nm were used to filtrate oil samples injected with different mole fractions of CO2 and CH4 gas. The distribution of asphaltene aggregates’ size at different injected CO2 and CH4 concentrations were obtained and compared with the pore size distribution data of shale cores measured by mercury intrusion porosimeters. Results showed that a higher injected CO2 and CH4 concentration caused more asphaltene precipitation and growth in asphaltene aggregates’ size. The precipitated asphaltene particle size was large enough to cause a pore-blocking problem in tested shale cores.
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Sabinas - Rio Grande Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (3 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale oil (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Precipitates (paraffin, asphaltenes, etc.) (1.00)
- North America > United States > West Virginia (0.44)
- North America > United States > Virginia (0.44)
- North America > United States > Pennsylvania (0.44)