High Pressure Temperature Conditions Research Articles

Strain-Induced Fabric Transition of Chlorite and Implications for Seismic Anisotropy in Subduction Zones

Seismic anisotropy of S-wave, trench-parallel or trench-normal polarization direction of fast S-wave, has been observed in the fore-arc and back-arc regions of subduction zones. Lattice preferred orientation (LPO) of elastically anisotropic chlorite has been suggested as one of the major causes of seismic anisotropy in subduction zones. However, there are two different LPOs of chlorite reported based on the previous studies of natural chlorite peridotites, which can produce different expression of seismic anisotropy. The mechanism for causing the two different LPOs of chlorite is not known. Therefore, we conducted deformation experiments of chlorite peridotite under high pressure–temperature conditions (P = 0.5–2.5 GPa, T = 540–720 °C). We found that two different chlorite LPOs were developed depending on the magnitude of shear strain. The type-1 chlorite LPO is characterized by the [001] axes aligned subnormal to the shear plane, and the type-2 chlorite LPO is characterized by a girdle distribution of the [001] axes subnormal to the shear direction. The type-1 chlorite LPO developed under low shear strain (γ ≤ 3.1 ± 0.3), producing trench-parallel seismic anisotropy. The type-2 chlorite LPO developed under high shear strain (γ ≥ 5.1 ± 1.5), producing trench-normal seismic anisotropy. The anisotropy of S-wave velocity (AVs) of chlorite was very strong up to AVs = 48.7% so that anomalous seismic anisotropy in subduction zones can be influenced by the chlorite LPOs.

The seismically fastest chemical heterogeneity in the Earth's deep upper mantle—implications from the single-crystal thermoelastic properties of jadeite

Jadeite is a major mineral phase (up to 50 vol%) in the subducted sediments/crust with continental origin, which are one of the major heterogeneities and important enriched geochemical reservoirs (such as EM-1 and EM-2) for incompatible elements in the Earth's interior. Identifying and locating the enriched geochemical heterogeneities requires knowledge of the elastic properties of relevant mineral phases at high pressure-temperature conditions. Unfortunately, the single-crystal elastic properties of jadeite have never been measured at high-pressure conditions, partially due to its low crystal symmetry. In this study, we have experimentally determined the single-crystal elastic moduli of jadeite at high pressures for the first time up to 18 GPa at the ambient temperature condition using Brillouin spectroscopy. Fitting the third-order finite strain equation of state to the velocity-pressure data yields KS0′=3.9(1), G0′=1.09(4) with ρ0=3.302(5) g/cm3, KS0=138(3) GPa, and G0=84(2) GPa. In addition, we have also conducted synchrotron single-crystal X-ray diffraction experiments up to 25 GPa and 700 K. The fitting of a Holland-Powell type thermal-pressure Birch-Murnaghan equation of state yields KT0′=3.8(2) and α0=3.4(5) ×10−5 K−1. Based on the obtained thermoelastic parameters of jadeite, the density and seismic velocities of continent-derived sediments/crust are modeled at the depth range from 200 to 500 km. The seismic velocities of the subducted continental sediments/crust become extremely fast at depths greater than ∼300 km, up to 11.8% and 14.7% faster than the Vp and Vs of the ambient mantle, and 5.6% and 7.3% faster than the Vp and Vs of the subducted oceanic crust. The existence of even a small amount of the subducted continental sediments/crust can result in strong seismic anomalies in the Earth's interior.

Gated detection of supercontinuum pulses enables optical probing of solid and molten silicates at extreme pressure-temperature conditions.

Optical studies of materials at high pressure-temperature (P-T) conditions provide insights into their physical properties that may be inaccessible to direct determination at extreme conditions. Incandescent light sources, however, are insufficiently bright to optically probe samples with radiative temperatures above ∼1000 K. Here we report on a system to perform optical absorption experiments in a laser-heated diamond anvil cell at T up to at least 4000 K. This setup is based on a pulsed supercontinuum (broadband) light probe and a gated CCD detector. Precise and tight synchronization of the detector gates (3 ns) to the bright probe pulses (1 ns) diminishes the recorded thermal background and preserves an excellent probe signal at high temperature. We demonstrate the efficiency of this spectroscopic setup by measuring the optical absorbance of solid and molten (Mg,Fe)SiO3, an important constituent of planetary mantles, at P ∼30 GPa and T ∼1200 K to 4150 K. Optical absorbance of the hot solid (Mg,Fe)SiO3 is moderately sensitive to temperature but increases abruptly upon melting and acquires a strong temperature dependence. Our results enable quantitative estimates of the opacity of planetary mantles with implications to their thermal and electrical conductivities, all of which have never been constrained at representative P-T conditions, and call for an optical detection of melting in silicate-bearing systems to resolve the extant ambiguity in their high-pressure melting curves.

Barite\u2013Micromax mixture, an enhanced weighting agent for the elimination of barite sag in invert emulsion drilling fluids

Weighting agents are mixed with the drilling mud to provide the high density required to control high-pressure high-temperature (HPHT) wells throughout the drilling operation. Solids sag occurs when the weighting agent separates from the liquid phase and settles down, causing variations in the drilling fluid density. This study evaluates barite–manganese tetroxide (Micromax) mixture to eliminate solids sag issue encountered with weighted invert emulsion drilling fluids at HPHT conditions. Micromax additive was added to barite-weighted fluids in different concentrations, 0, 15, and 30 wt% of the total weighting agent. Static and dynamic sag tests were used to evaluate the sag tendency of the new formulation under static and dynamic conditions. The performance of the new formulation was evaluated by measuring the electrical stability, density, rheological, viscoelastic, and filtration properties of the drilling fluid. The obtained results showed that Micromax additive improves drilling fluid stability by reducing the sag tendency. Adding only 30 wt% of Micromax additive eliminated barite sag issue in both dynamic and static conditions at 350 °F. 30 wt% Micromax increased the base fluid density by 5.4% and the yield point by 115% and maintained the gel strength value at 12 lb/100 ft2, while it reduced the plastic viscosity by 30%. The addition of Micromax additive improved the viscoelastic properties of the drilling fluid by maintaining a higher storage modulus to the loss modulus ratio when compared with the barite sample (in the range 4–4.5). Furthermore, 30 wt% Micromax improved the filtration performance by reducing the filtrate volume, filter cake weight, and filter cake thickness by 50%.

Problems Analysis on Preparation of Oil and Gas Drilling Rig Installation for Next Operations Readiness after HPHT (High Pressure High Temperature) Well Operation

Oil and gas drilling is an activity designed to bring oil and gas resources into the surface of the earth using drilling rig. One of the characteristics of drilling wells is HPHT (High-Pressure High Temperature) condition, where this type of well can reach temperature of 150 °C and pressure of 15,000 psi. Due to these extreme conditions, the drilling rig installation often need to be serviced after it operates under HPHT condition before it can be operated again. The influences of HPHT wells conditions to the equipment component in the drilling operation systems are studied to find out the probable failures root cause that make the drilling rig break down and have significant Non-Productive Time (NPT) after operated on HPHT well. During this study, we found out that the root cause of the problem is failed to apply a detailed requirements in SOP and Operation Manual as a provision of drilling operation. The problems become more significant for the rig performance and its NPT thus affecting the overall drilling program and company revenue.

Effects of Waxes and the Related Chemicals on Asphaltene Aggregation and Deposition Phenomena: Experimental and Modeling Studies.

Solid deposition during production, transport, and storage of crude oils leads to significant technical problems and economic losses for the oil and gas industry. The thermodynamic equilibrium between high-molecular-weight components of crude oil, such as asphaltenes, resins, and waxes, is an important parameter for the stability of crude oil. Once the equilibrium is disturbed due to variations in temperature, pressure, and oil composition during production, the solubility of high-molecular-weight waxes decreases. This results in a decrease in the wax appearance temperature (WAT) and the deposit of wax onto solid surfaces. On the other hand, under these conditions, asphaltenes do not interact sufficiently with the resins/waxes and tend to flocculate among themselves and form asphaltene nanoaggregates. The role of waxes during the asphaltene aggregation and deposition has not been appropriately explained yet. The objective of this research study is to describe the interaction of asphaltenes and waxes and subsequently address the specific example of an asphaltenic oil commingled with a wax inhibitor-containing oil during the combination of different oil streams. It is a crucial building block for the development of a suitable and cost-effective strategy for the handling of wax/asphaltene associated flow assurance problems. In this work, the quartz crystal microbalance (QCM) technique has been used for the first time to investigate the effect of waxes and related chemicals, which are used to mitigate wax deposition, on asphaltene aggregation and deposition phenomena. Asphaltene onset point and asphaltene deposition rate have been monitored using QCM at high pressure–high temperature (HPHT) conditions. This study confirms that the different wax inhibitor chemistries result in significant differences in the pour point decrease and viscosity profiles in crude oil. Different wax inhibitors also showed different outcomes regarding the asphaltene deposition tendency. A comprehensive modeling study has also been conducted for mechanistic investigation of experimental results. In this regard, the perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) was utilized to model the systems.

A Field Case Study of Managed Pressure Drilling in Offshore Ultra High-Pressure High-Temperature Exploration Well in the South China Sea

Summary The Y basin in the South China Sea has 15 trillion m3 of natural gas and represents typical ultra high-pressure high-temperature (ultra-HPHT) subsurface conditions, with the maximum bottomhole pressure (BHP) of 142 MPa (equivalent density = 2.38 sg), the highest bottomhole temperature (BHT) of 249°C at a depth of 5638 m, and an extremely narrow drilling mud density window. Therefore, there are several kinds of technical challenges during drilling operations. In recent years, managed pressure drilling (MPD) has been successfully applied in the basin with reduction of risks and well cost. Presented research focuses on a successful field case study of MPD in the Y basin. The case study consisted of two parts: MPD operational designs and MPD operational procedures. MPD operational designs included two steps: the precise calculation of drilling fluid equivalent circulating density (ECD) and the optimization of operational parameters. Four models were used in calculating drilling fluid ECD: wellbore heat transfer model, drilling fluid equivalent static density (ESD) model, drilling fluid rheological property model, and incorporating the effects of cuttings in the pressure loss model. The second step included two key operational parameters: mud weight (MW) and surface backpressure (SBP). MPD operational procedures were performed in three steps: roles and responsibilities of key personnel during MPD operations, wellsite training program and emergency procedures. Emergency procedures included unexpected drilling events, downhole equipment failures, and surface equipment failures. Taking X-1 Well as an example from the field case study, the following important observations were made. First, the MPD equipment was installed after remodeling of the drilling platform, installation of the wellhead assembly, and pressure testing of the MPD equipment. Next, the MW was set to 2.15 sg and the SBP was maintained at 525 psi while drilling the 8⅜ in. hole section on the basis of the operational design. In addition, the possible risks and corresponding preventive measures were taken into account and the MPD casedhole fingerprinting exercises were carried out. Finally, the MPD was successfully applied to X gas field featuring offshore ultra-HPHT. In addition, the dynamic formation integrity test (DFIT) and stripping out of hole with SBP were conducted. The well was successfully drilled in the narrow drilling mud density window of 0.05 sg without incidents and a sharp drop in the nonproductive time (NPT) was observed. Also, the casing structure was optimized from 7 to 5 strings with a significant reduction in the well cost and drilling time.

Elasticity of single-crystal Fe-enriched diopside at high-pressure conditions: Implications for the origin of upper mantle low-velocity zones

AbstractDiopside is one of the most important end-members of clinopyroxene, which is an abundant mineral in upper-mantle petrologic models. The amount of clinopyroxene in upper-mantle pyrolite can be ∼15 vol%, while pyroxenite can contain as high as ∼60 vol% clinopyroxene. Knowing the elastic properties of the upper-mantle diopside at high pressure-temperature conditions is essential for constraining the chemical composition and interpreting seismic observations of region. Here we have measured the single-crystal elasticity of Fe-enriched diopside (Di80Hd20, Di-diopside, and Hd-hedenbergite; also called Fe-enriched clinopyroxene) at high-pressure conditions up to 18.5 GPa by using in situ Brillouin light-scattering spectroscopy (BLS) and synchrotron X-ray diffraction in a diamond-anvil cell. Our experimental results were used in evaluating the effects of pressure and Fe substitution on the full single-crystal elastic moduli across the Di-Hd solid-solution series to better understand the seismic velocity profiles of the upper mantle. Using the third- or fourth-order Eulerian finite-strain equations of state to model the elasticity data, the derived aggregate adiabatic bulk and shear moduli (KS0, G0) at ambient conditions were determined to be 117(2) and 70(1) GPa, respectively. The first- and second-pressure derivatives of bulk and shear moduli at 300 K were (∂KS/∂P)T = 5.0(2), (∂2KS/∂P2)T = –0.12(4) GPa−1 and (∂G/∂P)T = 1.72(9), (∂2G/∂P2)T = –0.05(2) GPa−1, respectively. A comparison of our results with previous studies on end-member diopside and hedenbergite in the literatures shows systematic linear correlations between the Fe composition and single-crystal elastic moduli. An addition of 20 mol% Fe in diopside increases KS0 by ∼1.7% (∼2 GPa) and reduces G0 by ∼4.1% (∼3 GPa), but has a negligible effect on the pressure derivatives of the bulk and shear moduli within experimental uncertainties. In addition, our modeling results show that substitution of 20 mol% Fe in diopside can reduce VP and VS by ∼1.8% and ∼3.5%, respectively, along both an expected normal mantle geotherm and a representative cold subducted slab geotherm. Furthermore, the modeling results show that the VP and VS profiles of Fe-enriched pyroxenite along the cold subducted slab geotherm are ∼3.2% and ∼2.5% lower than AK135 model at 400 km depth, respectively. Finally, we propose that the presence of Fe-enriched pyroxenite (including Fe-enriched clinopyroxene, Fe-enriched orthopyroxene, and Fe-enriched olivine), can be an effective mechanism to cause low-velocity anomalies in the upper mantle regions atop the 410 km discontinuity at cold subudcted slab conditions.

The untypical high-pressure Zintl phase SrGe6

Abstract The binary strontium germanide SrGe6 was synthesized at high-pressure high-temperature conditions of approximately 10 GPa and typically 1400 K before quenching to ambient conditions. At ambient pressure, SrGe6 decomposes in a monotropic fashion at T = 680(10) K into SrGe2 and Ge, indicating its metastable character. Single-crystal X-ray diffraction data indicate that the compound SrGe6 adopts a new monoclinic structure type comprising a unique three-dimensional framework of germanium atoms with unusual cages hosting the strontium cations. Quantum chemical analysis of the chemical bonding shows that the framework consists of three- and four- bonded germanium atoms yielding the precise electron count Sr[(4bGe0]4[(3b)Ge−]2 in accordance with the 8 − N rule and the Zintl concept. Conflicting with that, a pseudo-gap in the electronic density of states appears clearly below the Fermi level, and elaborate bonding analysis reveals additional Sr–Ge interactions in the concave coordination polyhedron of the strontium atoms.

Engineering of high specific strength and low thermal conductivity cementitious composites with hollow glass microspheres for high-temperature high-pressure applications

Lightweight cement-based composites with high specific strength and low thermal conductivity are highly sought in the energy and construction industries. These characteristics are important in designing cement liners for high-temperature, high-pressure (HTHP) wells, in addition to those operating in permafrost. Similar attributes are also desirable in designing cementitious composites for energy efficient building envelopes. This work reports the results of an experimental campaign focused on engineering lightweight cementitious composites with hollow glass microspheres. It is demonstrated that the chemical stability of microspheres at HTHP conditions can be directly controlled by modulating the specific surface area and dissolution rate constant of supplementary siliceous additives. In addition to the stabilizing effect, such additives lead to the pore structure refinement and the enhancement of interfacial transition zone (ITZ). Introduced lightweight composites are capable of delivering significant load bearing capacity when normally cured, which is greatly increased by hydrothermal curing. Such high specific strength composites possess thermal conductivity below 0.3 W/mK at the oven dry density <1000 kg/m3 and cement dosage <400 kg/m3. This class of cementitious composites bears potential to enhance zonal insulation and well integrity, as well as increasing energy efficiency of building envelopes.

Metamorphic evolution of carbonate-hosted microbial biosignature

Microbial biosignature assemblages captured within mineral substrates experience extreme pressures (P) and temperatures (T) during rock burial and metamorphism. We subjected natural microbial biofilms hosted within thermal spring carbonate to six high pressure, high temperature (HPHT) conditions spanning 500 and 800 MPa and 200 to 550 °C, to investigate the initial petrographic transformation of organic and inorganic phases. We find biogenic and amorphous silica mineralises increasingly mature organic matter (OM) as temperature and pressure increase, with OM expelled from recrystallised calcite at the highest HPHT, captured within a quartz phase. Sulfur globules associated with microbial filaments persist across all HPHT conditions in association with microbially-derived kerogen. These data demonstrate how microbial material captured within chemically-precipitated sediments petrographically evolves in high grade rocks during their first stages of transformation.

Kutnohorite CaMn(CO3)2 crystal growth at high pressure-temperature

High quality kutnohorite CaMn(CO3)2 single crystals up to 100 μm in size were successfully achieved under high pressure-temperature (P-T) conditions. Electron microprobe analyses revealed the average wt% of CaO was 25.98% and that of MnO was 32.88%, correspondingly well to the ideal formula of Ca1.0Mn1.0(CO3)2. Accurate crystalline structural data were determined from single-crystal X-ray diffraction (XRD), with the R3 space group and R3c space group used to refine the crystal structure of CaMn(CO3)2. The Ca-O and Mn-O bond lengths were slightly different when using the R3 space group, which were clearly distinguished from those in the dolomite structure. Therefore, R3c is the most probable space group for the CaMn(CO3)2 crystal structure. Thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) showed that CaMn(CO3)2 decomposed from 620–750 °C, but only one endothermic peak was observed during the decomposition process. It indicated that the octahedral units in CaMn(CO3)2 have the same thermal stability due to the complete miscibility of Ca and Mn. The results of single crystal XRD and thermal analysis provided direct evidence that CaMn(CO3)2 has a calcitetype structure, not dolomite-type layered structure, which was in good agreement with the rigid model of rhombohedral carbonates.

The Birgitta Field, Block 22/19a, UK North Sea

Abstract Birgitta Field was discovered by well 22/19-1 which encountered a 230 ft gas–condensate column in Triassic Skagerrak Formation and tested at a combined rate of 38.3 MMscfgd and 3750 bcpd. The tilted-fault block trap forms the crest of a Triassic ‘pod’ or mini-basin formed by salt withdrawal during Triassic extension, further rotated and eroded during Jurassic extension. Field extent is supported by apparent seismic hydrocarbon indications. An early oil charge was likely converted to condensate by Plio-Pleistocene gas influx and rapid burial, whilst an underlying palaeoresidual gas column reflects some trap leakage. Birgitta typifies certain Triassic reservoir characteristics in this part of the Central North Sea. The thick, relatively high net:gross reservoir comprises moderate to poorly sorted, sub-lithic to sub-arkosic sandstones deposited in a dryland braided fluvial system. Pore-lining chlorite overgrowths dominate the pore fabric, reducing pore throat sizes and contributing to appreciable levels of non-effective micro-porosity and hence elevated water saturation. Key petrophysical challenges are the accurate determination of effective porosity and water saturation. Birgitta approaches high pressure–high temperature conditions and illustrates some of the challenges of progressing small, unappraised field tie-backs. These include resource uncertainty, compartmentalization risk, infrastructure access and marginal economics. Evaluated for development several times, Birgitta presently remains undeveloped.

On the development of experimental methods to determine the rates of asphaltene precipitation, aggregation, and deposition

Despite the efforts throughout the last few decades, asphaltene deposition remains as one of the greatest challenges in the petroleum industry. In this work, we present a comprehensive series of experimental studies to better understand the asphaltene precipitation, aggregation, and deposition mechanisms. Here, we introduce a simple method to determine the amount of precipitated asphaltene using NIR spectroscopy measurements without the implementation of calibration curves. Moreover, the kinetics of asphaltene precipitation and aggregation is simultaneously investigated by a newly developed, fast, and reliable NIR spectroscopy technique. In the new method, only less than 2 ml of sample is required for each experiment. In addition, unlike gravimetric techniques, less time consuming and labor-intensive measurements can be performed. In addition, the temperature can be controlled; hence, experiments can be conducted to evaluate the effects of temperature and the driving force on the kinetics of asphaltene precipitation and aggregation. Subsequently, the quantified precipitated asphaltene amount can be used to calibrate the precipitation and aggregation kinetic parameters of the asphaltene deposition model. The results obtained from the kinetics experiments facilitate in establishing a function to scale the precipitation kinetic parameter from laboratory-scale experiments to real field high-pressure high-temperature conditions. Additionally, a multi-section stainless steel packed bed column is proposed to study asphaltene deposition at high temperature and under dynamic conditions. In these experiments, the amount of deposited asphaltene is directly quantified. The results from the packed bed column deposition tests can be used to calibrate the deposition kinetic parameter of the asphaltene deposition model.

Improving the rheology, lubricity, and differential sticking properties of water-based drilling muds at high temperatures using hydrophilic Gilsonite nanoparticles

Recent developments in nanofluids indicate that the addition of nanoparticles to water-based drilling muds can alleviate many drilling problems, including wellbore instability, lost circulation, torque and drag force, differential pipe sticking, and low drilling rates. In this study, the addition of hydrophilic Gilsonite nanoparticles (HGNs) to water-based drilling mud was investigated, and its effects upon the well-cleaning process, rheological properties, filtration loss reduction, lubricity characteristics, and, more importantly, on the differential sticking of the base fluid were evaluated. Hence, initially, the HGNs were characterized by means of Fourier transform infrared spectroscopy, the dynamic light scattering technique, as well as thermogravimetric and differential thermogravimetric analysis. The results showed that after the addition of HGNs, the rheological behavior of the base mud before the hot roll process was improved, and, interestingly, after the hot roll at 149 °C and 4 h, the characteristics of the sample mud were significantly retained, compared to those of the base mud. Also, after the hot roll, the plastic viscosity (PV) improved, the yield point (YP) was remarkably maintained, and the ratio of YP/PV was enhanced. On the other hand, the American Petroleum Institute (API) filtration loss was reduced by 36%, and, additionally, after the hot roll process, the filtration loss reduction and the mud cake thickness in high-pressure high-temperature conditions diminished by 79.4% and 50%, respectively. After the hot rolling process, the lubricity coefficient and torque percentage dropped by 15% and 13.63%, respectively. Also, the HGNs reduced the differential sticking coefficient and increased the likelihood of differential sticking release of the base fluid by 61.5%.

Experimental Analysis of &lt;i&gt;Persea americana&lt;/i&gt; as Filtration Loss Control Additive for Non-Aqueous Drilling Fluid

Persea Americana is well known for its short shelf life while the seed is widely considered a waste material by domestic consumers and industry processors. This paper presents the results of the study carried out to evaluate the possibility of using three parts of the Persea Americana namely: its seed, a combination of the Persea Americana seed and its pulp and the Persea Americana pulp as filtration loss control additives in a non-aqueous drilling fluid while using Sodium Asphalt Sulfonate as a control. The evaluation was conducted under high pressure, high temperature (HPHT) static filtration test conditions (at 250°F and 500 psi) based on American Petroleum Institute Standard. From the study, the result showed that all three samples from the Persea Americana fruit showed good potential to control filtration loss when used to formulate a synthetic oil based mud. The filtration control capacity increased as their concentration in the mud was increased. However, in comparison, the pulp was 2.5 times and 1.5 times more efficient in controlling filtration loss when compared to the seed only and the seed and pulp combination respectively. Also, in terms of filtrate volume and filtered cake thickness, an equal concentration of Sodium Asphalt Sulfonate and the proposed additive gave good results; but the existing filtration loss control additive is slightly better than the proposed one. The low fluid loss volumes recorded with Persea Americana as fluid loss additives at HPHT conditions is an indication of its stability at elevated temperature conditions. The cake thickness was thin, impermeable and 1mm in size for all the samples of the Persea Americana. This meets the API requirement of mud cake thickness of less than 2mm.

Nano-fluid viscosity screening and study of in situ foam pressure buildup at high-temperature high-pressure conditions

In this study, an industrial-based surfactant known as MFomax surfactant has been modified with unfunctionalized and silane-functionalized silica nanoparticles (NPs) to select the high viscous nano-fluid (NF) for generation of in situ foam to assess the differential pressure buildup (∆p) behavior in the porous media. Different weight concentrations of NPs and MFomax from 0.1 to 0.5% were studied using Design Expert Software to generate full matrix design of NF formulations. The viscosity data were analyzed with the aid of response surface analytical tool to investigate the response of NPs loading on the NF viscosity for optimization. The microstructural properties of the NFs were characterized using spectroscopic equipment. Subsequently, the high viscous NF was selected to generate in situ foam in comparison with the precursor MFomax foam for ∆p buildup assessment at 110 °C and 2023 psi in the native reservoir core. Results have shown that both the silica NPs could significantly improve the MFomax viscosity; however, the silane-functionalized silica NPs have more effect to improve the viscosity and other microstructural properties than the unfunctionalized NPs, and thus, they were selected for further experimental studies. The coreflood ∆p buildup assessment shows that NF foam built more ∆p having average value of 46 psi against 25 psi observed in the case of the precursor MFomax foam. Thus, this study demonstrates that functionalized silica NPs could improve the MFomax viscosity and eventually generates high ∆p buildup at high-temperature high-pressure conditions.

Design of a containment apparatus for synchrotron XAS measurements of radioactive fluid samples under high temperatures and pressures.

The simple working principles and versatility of the hydrothermal diamond-anvil cell (HDAC) make it highly useful for synchrotron x-ray studies of aqueous and fluid samples at high pressure-temperature (P-T) conditions. However, safety concerns need to be overcome in order to use the HDAC for synchrotron studies of aqueous radioactive samples at high temperatures and pressures. For accomplishment of such hydrothermal experiments of radioactive materials at synchrotron beamlines, the samples are required to be enclosed in a containment system employing three independent layers of airtight sealing at some synchrotron facilities while enabling access to the sample using several experimental probes, including incoming and outgoing x-rays. In this article, we report the design and implementation of a complete radiological safety enclosure system for an HDAC specialized for high P-T x-ray absorption spectroscopy (XAS) measurements of aqueous solutions containing the actinides at synchrotron beamlines. The enclosure system was successfully tested for XAS experiments using the HDAC with aqueous samples containing depleted uranium at temperatures ranging from 25 to 500 °C and pressures ranging from vapor pressure to 350 MPa.

Emerging challenges in phase behavior modeling of reservoir fluids at high-pressure high-temperature (HPHT) conditions

Global energy demand is driving the oil and gas industry to explore uncharted areas leading to unconventional reservoirs at extreme temperature (T > 420 K) and pressure (P > 68 MPa) conditions where widely used equations of state (EOS) models fail to accurately predict properties of reservoir fluids and model their phase behavior. This work compares promising and adaptable EOS models for HPHT systems, highlighting their concomitant shortfalls in specified scenarios which need to be addressed by researchers in the quest for accurate predictive tools at extreme T and P reservoir conditions. Five EOS models were used for density prediction for n-heptane at 323 K and 423 K over a pressure range of 28–270 MPa where PC SAFT emerged the overall best. At 520 K however, VT PR-EOS and VT SRK-EOS performed better. For a binary system of C3/nC10, PC SAFT, which was highly promising, began to drop in accuracy with increase in temperature from 277 to 510 K. Furthermore, four EOS were tested for volume and z-factor prediction of pure systems (C1–C6) and their binaries. While PC SAFT is most promising, significant drawbacks are evident when applied to binary systems and are expected to worsen with increase in number of constituents. It was made clear that a pressure-dependent correction factor will significantly improve the accuracy of the PC-SAFT model. Suggestions on novel alternative routes for EOS model development and improvement are also given.

Synthesis and characterization of hydrophilic gilsonite fine particles for improving water-based drilling mud properties

In this study, hydrophilic gilsonite fine particles were produced by reaction of natural gilsonite with a mixture of sulfuric acid and nitric acid followed by a planetary ball mill process. The hydrophilic gilsonite was characterized using FTIR, XRD, FE-SEM, DLS, elemental analysis, and mass spectroscopy. All experiments showed that the characteristics of the hydrophilic gilsonite, due to its surface modification, were different from those of natural gilsonite. Moreover, hydrophilic gilsonite molecules were dispersed in water as fine particles with an average diameter of 300 nm without adding any dispersant. The effects of hydrophilic gilsonite on the rheological properties as well as the fluid loss of the water-based drilling mud were investigated before and after the hot-roll process. The results showed that simultaneous adding of 10 g of hydrophilic gilsonite fine particles to the base fluid and reducing the starch concentration to half of its initial value resulted into the best composition for efficient water-based drilling mud. In this case, the rheological properties of the mud were stabilized with a minimum change in the decrease of the yield point, foam formation was prevented after the hot-roll process, and the pH of the system was stabilized in a suitable range at high temperatures. Moreover, this composition could reduce the fluid loss by 50.8% and the filter cake thickness by 66.7% in low-temperature, low-pressure conditions, while the fluid loss reduction was 75% in high-temperature high-pressure conditions. Moreover, the results revealed that hydrophilic gilsonite was an effective additive during the 16 h hot-roll process.