Overcoming Wax Deposition Challenges Using Heated Online Sand Sampling for Reliable Sand Surveillance: A Case Study from Malaysia

Waxy crude oils are normally found in petroleum reservoirs. Crude oil with the wax formation is one of the crucial problems for flow assurance of pipeline transportation in oil and gas production. This issue can commonly cause wax deposition problem and it has made a huge amount of economic losses such as production, time and maintenance cost. Therefore, it is a critical aspect to deal with wax deposition for crude oil flow assurance, especially at the surface region in cold climate. In this study, n-heptane and poly (maleic anhydride-alt-1-octadecane) or MA as the inhibitors with different concentrations will be measured the effect on pour point, wax appearance temperature and wax deposition of Mae Soon crude oil and investigated the effects of parameters such as temperature, concentration and types of inhibitors for these aspects.
 
 N-heptane plays a key role in the reduction of pour point, wax appearance temperature and wax deposition of this study.� It is also found that the amount of total wax deposits decreases when this chemical concentration increases. Consequently, an increasing concentration provides a better performance for inhibition of wax deposition problems.�On the other hand, MA also shows the results for the reduction of wax appearance temperature and wax deposition of Mae soon crude oil. According to the results, it offers low performance for pour point reduction because it cannot be soluble well in the higher wax content of crude oil. After each individual inhibitor are measured for the reduction of pour point, wax appearance temperature and wax deposition, the mixtures of n-heptane and MA are investigated to have better results for wax deposition prevention. It is found that 10% n-heptane and 5000 ppm MA provides the optimal condition for wax deposition prevention based on this study because it can show low wax deposition with less amount of chemical consumption. The results can be used as fundamental data and the investigation can expand into combination with another type of inhibitors.

A new perspective on the measurements of wax appearance temperature: Comparison between DSC, thermomicroscopy and rheometry and the cooling rate effects

Characterization of the wax precipitation in Iranian crude oil based on Wax Appearance Temperature (WAT): Part 1. The influence of electromagnetic waves

Wax appearance temperatures of vegetable oils determined by differential scanning calorimetry: effect of triacylglycerol structure and its modification

A microfluidic technique for measuring wax appearance temperature (WAT) of reservoir fluids is presented. The technique is based on continuous monitoring of pressure across a microchannel as wax particles are deposited and gradually clog the channel. A rapid pressure increase was observed as the temperature was systematically decreased to wax appearance temperature. The relationship between pressure change rate and sample temperature is explored as the working principle in the proposed WAT measurement technique. This technique yields results which are comparable to measurements obtained from a cross-polar microscopy technique (CPM); the current industry-standard for WAT measurement. The method is validated by systematically investigating phase transition of pure hydrocarbons, binary mixtures, and real crude oils. The new technique has two distinct advantages over the existing industry standard methods in that its experimental setup is much simpler and it can be adapted to field applications. The microchannel can be easily cleaned and reused to test different samples.

Paraffin wax deposition is the most frequent flow assurance problem in oil production fields. It disrupts stable oil production, and a considerable amount of time and money are spent ameliorating on-site problems. To prevent and mitigate paraffin wax deposition, it is necessary to proactively identify the conditions under which paraffin wax is deposited. Furthermore, monitoring and detection techniques are required to determine the efficacy of the technical measures applied. This study proposes a method based on acoustic velocities obtained by ultrasonic monitoring and detection to estimate the following three temperature elements: (1) wax appearance temperature of oil containing paraffin wax, (2) temperature at which the growth of paraffin wax deposits is activated, and (3) temperature at which the paraffin wax deposits begin to age. An experimental system comprising an ultrasonic transducer and a temperature sensor were set up, and the temperature gradient of the analyzed fluid sample was controlled by continuously circulating an isothermal fluid. Based on real-time monitoring, data measurements were made, and variations in the acoustic velocity of fluid samples were measured. A paraffin wax deposition experiment was conducted using synthetic waxy oil samples with paraffin solid contents of 5 wt.% and 15 wt.%, respectively. Q-factors were calculated based on the spectral ratio method, and wavelet characteristics were analyzed according to temperature changes, to estimate wax appearance temperature. Results show that the method proposed in this study estimates wax appearance temperature in a similar measurement range as conventional methods and enables the life cycle of paraffin wax deposition to be determined through monitoring and detection.

Wax appearance temperature (WAT) determinations of different origin crude oils by differential scanning calorimetry

Foaming characteristics of crude oil-CO2 mixture by depressurization: Influence of crude oil viscosity and wax precipitation

Wax appearance temperature (WAT) of live oil is a key index for determining the reasonable injected water temperature of high waxy oilfield. In view of the difference of the oil composition and pressure between live oil and dead oil under reservoir conditions, aiming at the practical problems such as the limitation to dead oil of the normal test method at home and abroad, based on the response of the ultrasonic parameters such as transit time, amplitude and frequency during waxy participation, a novel ultrasonic detection system used for the wax participation characteristics was designed. Taken typical oil samples of kingfisher oilfield as an example, WAT, amount of wax participated and dynamic wax participation process of both dead and live oil under different pressures were studied, respectively. Results showed that there exist two main stages for the wax participation process: nucleation and growth. The existence of the dissolved gas decreases the WAT significantly. The higher the pressure, the higher the WAT for the oil above the saturation pressure. Transit time, amplitude and frequency could all be used as sensitive parameters to estimate the WAT, amount of wax participated and dynamic wax participation process.

Experimental investigation of the live oil-water relative permeability and displacement efficiency on Kingfisher waxy oil reservoir

Ionic liquids are assessed as chemical additives to modulate physical properties of oils. Rheometry, differential scanning calorimetry, thermogravimetric analysis and microscopy are used to investigate the effect of ionic liquids on oil properties. The measured maximum apparent viscosity value of Model Oil A increases by 178.7% in the presence of 1 wt% 1-butyl-3-methylimidazolium chloride. Similarly, the value increases in the presence of other conventional ionic liquids. However, the dispersed property of ILs in Model Oil A is not as good as expected. Thus, dispersant D-IL-202 is utilized to make ionic liquids dispersed completely in Model Oil A and form Model Oil B. The gel strength and maximum measured apparent viscosity of Model Oil B increase by 477.4%, 352.4% respectively in the presence of 1 wt% 1-butyl-3-methylimidazolium chloride. Wax crystals precipitate at temperature below wax appearance temperature. The melting point of 1-butyl-3-methylimidazolium chloride is higher than wax appearance temperature. Therefore, during the gelation process, the precipitated crystals of 1-butyl-3-methylimidazolium chloride may serve as nuclei and enhance wax crystal nucleation, precipitation and growth. In addition, the charges of 1-butyl-3-methylimidazolium chloride may make the precipitated wax crystals form a charge-stabilized colloids system. Thus, strong and stable crystal networks form during the gelation process. 1-Butyl-3-methylimidazolium chloride can be utilized as a wax promoter additive for wax separation from waxy oils in the oil industry. Thermogravimetric analysis shows 1-butyl-3-methylimidazolium chloride does not influence the decomposition temperatures of wax and asphaltene. However, the decomposition temperature of 1-butyl-3-methylimidazolium chloride increases in the presence of wax and decreases in the presence of asphaltene. Furthermore, micrographs results show 1-butyl-3-methylimidazolium chloride enhances wax precipitation to make long wax crystals form. In summary, the conventional ionic liquids used in this work can enhance the wax precipitation and/or stabilize the wax crystal networks. Thus, these ionic liquids can be utilized as a wax promoter additive for wax separation in the waxy oil industry. In addition, the property and function of ionic liquids can be designed and modified to be utilized as novel additives for oil properties modulation. Therefore, ionic liquids are promising environmentally friendly additives for the oil industry.

The development of pre-salt fields in the Santos Basin has presented a plenty of technological challenges, which include the production of fluids with high values of GOR (Gas Oil Ratio) and high values of WAT (Wax Appearance Temperature). To avoid the wax deposition, it is absolutely imperative handling the temperature by insulation and/or heating. If in one hand the production system thermal insulation minimizes the heat losses to the environment, on the other hand the cooling due the thermodynamic effect of gas expansion is inevitable, mainly in fields with high GOR values. To mitigate the problem of temperature drop, mainly in the risers where the expansion effects are pronounced, various heating systems for subsea pipelines have been studied by PETROBRAS. In parallel to these studies, it was noted that the design philosophy of the offshore production units for the pre-salt fields have indicated the use of turbo–generators to supply electrical power to the production unit, leading to the opportunity of using the generated super heated gases, originally discharged into the atmosphere, in order to feed the riser heating systems based on heated fluids circulation. Studies of heat exchange performed indicated a great potential for the risers heating by the flow of heated water through the annular of a Pipe-in-Pipe riser, by using a WHRU (Waste Heat Recovery Unit) to recover the power discharged into the atmosphere from the turbo–generators. It was identified the possibility of heating Pipe-in-Pipe risers by circulating heated fresh water in a closed loop with water return to the production unit, or by coupling the riser heating system with the water injection system, using all the facilities for treatment and pumping of water injection. This paper aims to describe the methodology considered in the development of a conceptual design of a heating system for a Pipe-in-Pipe riser, by the flow of heated water in the annular, in a Free Standing Hybrid Riser configuration. The paper will also present the characteristics associated with the two possibilities of heated water circuit, as well as advantages and disadvantages of each system, and the aspects related to subsea production layout.

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min−1. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min−1. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines.

An Oil reserve is discovered in a remote shallow water area offshore Africa, where the water depth is approximately 200 ft. The predicted production rate is approximately 500 BPD per well. The obtained oil samples indicate that the produced fluid has a high pour point (91°F) and a high wax appearance temperature (105°F). A dry tree completion is the planned option for this field. The wellhead flowing temperature (WHFT) is predicted to be below the wax appearance temperature (WAT) during normal flow without heating. Under certain specific field conditions, such as the development being considered, hot gas can be used as a means to maintain WHFT above the oil WAT and also be used as an artificial lift method to produce the low pressure / low temperature wells (LPLT). Economically, since the reserve is located remotely from gas market, the produced gas is "free." This paper describes the engineering evaluation of a hot gas lift design concept for a particular LPLT field. The hot gas lift method will avoid wax deposition, gelling and blockage problems in the wellbore. The wellbore thermal-hydraulic behavior is studied to optimize gas lift injection rates and temperature.

With the application of chemical enhanced oil recovery methods, water separation is a major issue in a production facility. Oil/water separation is suppressed with a stable emulsion. The present study evaluated the impact of different emulsifiers in enhanced oil recovery. The effectiveness of each additive such as an alkali, surfactant, or polymer on the stability of the emulsion was anticipated using laser scattering to measure the emulsion’s stability. An artificial neural network was applied to predict the effectiveness of the additives on stabilization/destabilization and to assess how alkali/surfactants, surfactant/polymers, and polymer/surfactants affect the separation profiles. Measurements of the viscosity and zeta potential of residual emulsion clarify that the increase in surfactant makes the emulsion stable and became unstable with the increase in the alkali and polymer. The droplet zeta potential was within −i9~−i5 mV. The absolute value of the zeta potential decreased at a high polymer concentration with a low surfactant concentration resulting in fast flocculence phenomena. With an increase in the surfactant concentration and the presence of high alkali, the droplet’s absolute zeta potential demonstrated an increase in the repulsion force in the emulsions. The study also focuses on the carbon number distribution, wax appearance temperature (WAT) and wax content of four crude oil samples from different field locations (Miri, Angsi, Penara and Dulang). Findings show that crude oil samples with higher mol percent of carbon distribution from C20 to C40 (paraffinic composition) contains higher wax content, wt% and subsequently results in higher wax appearance temperature (WAT). This is obviously shown by the crude oil sample from Penara field. Further similar investigation on other field locations will assist in characterizing the paraffinic composition in Malaysian oil basins.