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Dispersants, also known as friction reducers, are used extensively in cement slurries to improve the rheological properties that relate to the flow behavior of the slurry. Dispersants are used primarily to lower the frictional pressures of cement slurries while they are being pumped into the well. Converting frictional pressure of a slurry, during pumping, reduces the pumping rate necessary to obtain turbulent flow for specific well conditions, reduces surface pumping pressures and horsepower required to pump the cement into the well, and reduces pressures exerted on weak formations, possibly preventing circulation losses. Another advantage of dispersants is that they provide slurries with high solids-to-water ratios that have good rheological properties. This factor has been used in designing high-density slurries up to approximately 17 lbm/gal without the need for a weighting additive.
Traboulay, Vaughn Reza (Schlumberger) | Aung, Tint Htoo (Schlumberger) | Manzoleloua, Cedric (Schlumberger) | Panamarathupalayam, Balakrishnan (Schlumberger) | Arena, Carmelo (Schlumberger) | DMello, Allwyn (Schlumberger) | Sebelin, Linus (Schlumberger) | Eyaa, Clotaire (Schlumberger)
Abstract High-temperature water-based drilling fluid systems hold several advantages over synthetic based systems from financial and environmental viewpoints. However, most conventional water-based systems start to become unstable at temperatures above 300 degF. This paper details the design and implementation of A Novel Water-Based Drilling Fluid that meet these temperature stability requirements. The newly developed high-temperature water-based system discussed in this paper utilizes a custom-made branched synthetic polymer that exhibits superior rheological properties and fluid loss control as well as long term stability above 400 degF. The branched synthetic polymer is compatible with most oilfield brines and maintains excellent low-end rheology necessary for hole cleaning and solids suspension under high-temperatures and pressures. Under static conditions, the high-temperature fluid shows no gelation resulting in lower swab surge pressures while the stability of the highly branched synthetic polymer and enhanced rheological profile minimize sag. To drill a challenging exploration well, a Middle East client required a cost-effective drilling fluid system which remains stable under static temperatures expected to exceed 375 degF. The long-term stability of the system was critical for successful wireline logging operations. In addition, the system was required to provide shale inhibition, hydrogen sulfide suppression and sufficient density (above 16.5 lbm/galUS) to maintain well integrity while drilling through anticipated high-pressure zones. The challenging intermediate (12.25-in and 8.375-in) and reservoir (6-in) sections were successfully drilled and evaluated using this new branched synthetic polymer-based system. Fluid property trends and system treatments will be detailed alongside thermal stability data for extended periods required for wireline logging (up to 9 days static). This paper will discuss how proper laboratory design of the high-temperature water-based system was translated to excellent field performance and will indicate how this technology can be utilized for future campaigns in the region and worldwide.
Abstract All wells require casing strings so that the planned operations can proceed. Ensuring a good quality casing set is vitally important. When conducting the calculations for frictional pressure losses the casing couplings are not taken into consideration. In API calculation methodologies for drill pipe the effect of tool joints is not taken into calculation. However, the small clearance between the casing coupling and the hole size is definitely creating an additional frictional pressure drop in comparison to the calculated which under normal circumstances taken into account the nominal casing outer diameter (OD). In this study the effect of casing couplings is taken into consideration when calculating the annular frictional pressure losses to drive the Equivalent Circulating Density (ECD). The generally accepted frictional pressure loss equations are used for a variety of casing running scenarios. The methodology that is introduced in this research study is a step change for automation in drilling operations. The findings are used to compare with the conditions during which the effect of casing couplings is not taken into consideration. The general findings indicate that annular frictional pressure losses are very critical for all wells but especially for the wells with narrow drilling margins. This research study reveals that annular frictional pressure losses are very critical for the successful casing running operations not only during circulations through the casing string but also at the time of the cementing of the same. The introduced methodology that takes into consideration of casing couplings can be used for automation in drilling operations.
Kalhor Mohammadi, Mojtaba (International Drilling Fluids) | Taraghikhah, Shervin (International Drilling Fluids) | Karimi Rad, Mohammad Saeed (International Drilling Fluids) | Tahmasbi Nowtaraki, Koroush (International Drilling Fluids)
Abstract Developing high-performance environmentally friendly drilling fluids is always a requirement by oil and gas operators to reduce the waste management associated cost with the drilling fluid treatment and disposal. Conventional water-based drilling fluid is formulated with the brine-based polymer which consists of sodium and potassium chloride salts to improve the performance of the polymer and also providing clay inhibition in reactive clay and shale. This paper describes the development of nanotechnology-based drilling fluid to replace salt from the conventional application. Nano Based Low Saline Water Based Mud (NBLS-WBM) was formulated and developed based on laboratory experiments. Different nano additives with different concentrations were evaluated and the optimum concentration was selected to reduce the sodium and potassium chloride salts concentration to almost zero. The rheological properties and fluid loss were measured according to the API standard before and after hot rolling. Also, HPHT fluid loss, lubricity, and shale inhibition were evaluated. All the results were compared with sodium salt-saturated and potassium-based polymer muds. Laboratory evaluation of NBLS-WBM indicated that sodium salt concentration can be reduced considerably up to 5% W/V and potassium chloride can be eliminated by adding 1% W/W of nano additive. The rheological properties including plastic viscosity and yield point were constant and stable after hot rolling 16 hours at 250 °F. Also, Clay inhibition improved significantly up to 95% recovery comparing with conventional water-based polymer mud. Although the application of nanotechnology to improve the performance of conventional water-based drilling fluid was studied by many researchers, it is the novelty of this research to reduce the salt concentration and remove it to develop the new generation of salt-free water-based drilling fluid with economical consideration and lower environmental impact.
Zhong, Hanyi (China University of Petroleum, East China) | Kong, Xiangzheng (China University of Petroleum, East China) | Qiu, Zhengsong (China University of Petroleum, East China) | Huang, Weian (China University of Petroleum, East China) | Zhang, Xianbin (Tianjin Key Laboratory of Complex Conditions Drilling Fluid) | Zhao, Chong (Tianjin Key Laboratory of Complex Conditions Drilling Fluid)
Abstract Owing to superior temperature stability in comparison with water-based drilling fluids, oil or synthetic-based drilling fluids are generally preferred for high temperature and high pressure (HTHP) formations. However, the thermal degradation of emulsifiers and polymeric components under HTHP conditions that results in loss of rheological and filtration control, barite sag or even fluid phase separation also occurs. It is a challenge to sustain these properties stable under such harsh condition. Since nanoparticles have potential to provide better thermal stability, improved filtration loss as well as emulsion stability, the aim of this study is to investigate the effect of nano carbon spheres on the properties of oil-based drilling fluids under high temperature conditions. The nano carbon spheres were synthesized with the hydrothermal reaction of glucose. The influence of nano carbon spheres on the rheological, filtration, emulsion stability, settlement stability, as well as lubricity of a typical mineral oil-based drilling fluid with oil to water ratio of 80:20 was investigated before and after thermal aging at 180 and 200°C, respectively. The structure characterization showed that the uniform hard nano carbon spheres exhibited intermediate wettability. Laboratory performance test indicated that, for the oil-based drilling fluid, the addition of nano carbon spheres improved the rheological properties in terms of yield point and the ratio of yield point to plastic viscosity, which is beneficial for transporting of drilling cuttings. After thermal aging at 200 °C, the filtration loss volume was reduced as high as 70%, and desirable filter cake quality was obtained by incorporation of 1.0 wt% spheres, meanwhile the electrical stability was improved both before and after thermal aging. Furthermore, the fluid formulated with the nano carbon spheres generated better barite sag control. The polarizing microscope observation showed that the nano carbon spheres accumulated at the water-oil interface and formed a steric barrier which probably explained the reason of the above enhanced performance. The green synthetic routes and environmental friendly characteristics of the nano carbon spheres, in combination with the excellent properties suggested that the nano carbon spheres hold potential as multi-functional additives for formulating oil-based drilling fluids for HTHP drilling operations.
Summary Drilling technology in petroleum engineering is associated with problems such as high fluid loss, poor hole cleaning, and pipe sticking. Improvement of rheological and filtration properties of water-based drilling fluids (WDFs) plays a major role in resolving these drilling problems. The application of nanotechnology to WDF in the recent past has attracted much attention in addressing these drilling operations problems. In the present work, we investigate the application of natural aloe vera and CuO nanofluids combined as an additive in WDF to address the drilling problems. The nanofluids of three different concentrations of CuO nanoparticle (0.2, 0.4 , and 0.6 wt%) with aloe vera as a base fluid are prepared for this study by adopting a two-step method. The prepared nanofluids are characterized by their particle size and morphological characteristics. Conventional WDF (DF.0) is synthesized, and the prepared aloe-vera-based CuO nanofluid is added to the WDF to prepare nanofluid-enhancedwater-based drilling fluid (NFWDF) of different concentrations of nanoparticles, namely, 0.2 , 0.4, and 0.6 wt%. The prepared drilling fluid mixture is then characterized for its rheological and filtrate loss properties at various temperatures. Thermal stability and aging studies are performed for both WDF and NFWDF. The experimental results are then modeled using rheological models. The results reveal that aloe-vera-based CuO nanofluids improve the thermal stability and rheological properties of drilling fluid and significantly decrease the American Petroleum Institute (API) filtrate. Viscosity for WDF shows an approximately 61.7% decrease in heating up to 90°C. Further, the hot roll aging test causes a 63% decrease in the viscosity of WDF at 90°C. However, the addition of aloe-vera-based CuO nanofluids is found to aid in recovering the viscosities to a great extent. The fluid loss values before hot rolling are observed to be 6.6 mL after 30 minutes, whereas fluid loss values for the NFWDFs are found to be 5.9, 5.4, and 4.6 mL, respectively. The fluid loss value after hot rolling for the WDF is found to be 10.8 mL after 30 minutes, whereas fluid loss values for the NFWDFs are found to be 9.2, 8.5, and 7.7 mL, respectively. The rheological performance data of NFWDF project a better fit with the Herschel-Bulkley model and suggest improvement in rheological and filtration properties. There has been limited research work available in understanding the impact of aloe-vera-gel-based nanofluids in improving the performance of WDFs through the improvement of its rheological and filtration properties. This study aims to exploit the property of native aloe vera and CuO nanofluids combined together to enhance the rheological and filtration properties of WDF by conducting the tests both before and after hot rolling conditions. This study acts as an important precursor for developing novel additives for WDF to improve its rheological and filtration properties. This study is also expected to benefit the industry and solve the major challenges in deep-well drilling operations and high-pressure and high-temperature (HPHT) drilling operations.
Bazhaykin, S. G. (The Pipeline Transport Institute LLC) | Zhed, V. N. (The Pipeline Transport Institute LLC) | Tuhvatullina, A. R. (The Pipeline Transport Institute LLC) | Koern, R. R. (The Pipeline Transport Institute LLC) | Ahmetova, Z. H. (The Pipeline Transport Institute LLC)
The article examines the effect of the quantitative content of resins, asphaltenes and paraffin in oil on the pour point of oil. The effect of a depressant additive on the pour point of oil and the transition of its state from Newtonian to non-Newtonian is also shown. The process of paraffin crystals precipitation into the solution with a decrease in oil temperature and its transition from a Newtonian state to a non-Newtonian one is considered. It is noted that at a certain temperature, Newtonian oil turns into a colloidal solution and begins to acquire the properties of a non-Newtonian fluid. With a further decrease in temperature, the viscosity of the oil will increase, and the area of hysteresis loop between the shear rate and the magnitude of the shear stress increases. The effect of resins and asphaltenes on the process of oil cooling is considered. It is noted that neutral resins form true solutions with oil products, asphaltenes form suspensions and colloidal solutions. On the basis of a large number of previous experiments, it was found that the quantitative ratio of the mass of paraffin to the amount of resins and asphaltenes does not unambiguously determine the pour point of oil. It is shown that an increase in the pour point of oil with an increase in the paraffin content in it can be disturbed due to the qualitative ratio of resins, asphaltenes and paraffins, which leads to a depressant effect. The relationship between the pour point of oil and the critical transition temperature from Newtonian to non-Newtonian is also considered. The effectiveness of the depressant effect is manifested from the moment the oil transitions to the non-Newtonian state. It is assumed that under the influence of a depressant additive, the pour point and the critical temperature of the transition from Newtonian to non-Newtonian change by the same value. This assumption is based on experimental data obtained by various authors. The relevance of the results obtained is that technologically the temperature of the beginning of paraffin precipitation is more important than the pour point of oil. This is due to the fact that during the transition of oil to a non-Newtonian state, dynamic viscosity and static shear stress increase. Operation of the pipeline in the area of the non-Newtonian state of the liquid is impractical due to increasing losses and the threat of oil solidification when pumping is stopped.
This paper describes a low-impact, nonaqueous drilling fluid (LIDF) designed to minimize equivalent circulating density (ECD) increases and associated risks in deep water by reducing the effect of cold temperature on fluid viscosity. The fluid offers a superior low-viscosity profile and rapid-set, easy-break gel strengths while maintaining low shear-rate viscosity at high temperatures with optimal-weight material suspension. Field application demonstrated that the LIDF reduced the effect of temperature on the fluid rheological properties and minimized the risk of induced formation losses. These same rheological features reduced nonproductive time (NPT) associated with cement displacement and barite sagging. The extreme conditions to which an offshore drilling fluid is subjected pose numerous challenges to achieving appropriate formulation.
This work focuses on using custom-made (CM) magnetite (Fe3O4) nanoparticles (NPs) to improve the properties of bentonite-based fluids. The microstructure qualities and modes of interaction have been identified, helping to optimize the rheological and fluid-loss properties of these drilling fluids. The better performance of the CM Fe3O4 NPs can be attributed to their extremely small size, which leads to stability in suspensions and effective linking with the bentonite particles, thus allowing the formation of a rigid microstructure network. The effects of adding iron oxide NPs on the rheological and filtration properties of aqueous bentonite suspensions have been studied by several researchers. The results showed that the addition of iron oxide NPs at low concentrations significantly improves drilling-fluid-filtration characteristics and maintains optimal rheological properties compared with the base fluid (BF).