High-pressure High-temperature Environments Research Articles

Exploring technological and operational challenges in high-pressure: High-temperature drilling techniques

This comprehensive review explores the complex landscape of HPHT drilling, examining the underlying principles, innovative technologies, and operational strategies used to overcome challenges such as wellbore stability, fluid management, equipment reliability, and downhole conditions. By understanding and addressing these challenges, the oil and gas industry can advance HPHT drilling capabilities and unlock new sources of energy to meet growing global demand. High-pressure, high-temperature (HPHT) drilling techniques have become indispensable for the oil and gas industry to tap into deep hydrocarbon reservoirs located in challenging environments. Despite their significance, HPHT drilling operations pose a myriad of technological and operational challenges that demand meticulous attention to safety, efficiency, and success. This comprehensive review embarks on an exploration of the intricate landscape of HPHT drilling, delving into the fundamental principles, innovative technologies, and operational strategies pivotal in surmounting obstacles such as wellbore stability, fluid management, equipment reliability, and downhole conditions. The review begins by delineating the distinctive characteristics of HPHT environments, highlighting the formidable challenges inherent in drilling operations conducted under extreme pressures and temperatures. Subsequently, it elucidates the critical importance of maintaining wellbore stability amidst such conditions, elucidating the risks of collapse and blowouts and offering insights into mitigation strategies ranging from meticulous drilling fluid selection to advanced wellbore monitoring techniques. Fluid management emerges as a focal point, as the review navigates through the complexities of selecting, formulating, and managing drilling fluids tailored for HPHT environments. Innovative technologies such as nanotechnology applications and synthetic-based mud systems are explored for their efficacy in addressing fluid-related challenges and enhancing drilling performance. The reliability and integrity of equipment constitute another critical aspect examined in the review, with emphasis on mechanical challenges, material selection, and proactive maintenance strategies essential for safeguarding equipment performance and longevity in HPHT operations. Furthermore, the review presents case studies and best practices gleaned from successful HPHT drilling projects, offering valuable insights and lessons learned to inform future endeavors.

Improving filter cake sealing properties for high-density ilmenite drilling fluid

Drilling fluids must be cautiously designed to form an impermeable filter cake layer that diminishes the intensity of solid and mud invasion during drilling of a well. Inability to abate solid and mud invasion can cause adverse effects on the productivity of the drilled well. As a result, a variety of additives have been proposed for improving filter cake's sealing properties, which are also utilized to control fluid filtration. This work investigates the role an amorphous volcanic glass (perlite), a novel filtration agent, to amend the quality of filter cake layer that formed using ilmenite (FeTiO3) drilling fluid. The characteristics of the filter cake were evaluated in terms of the filtration behavior, filter cake thickness, permeability and porosity. In order to accomplish this aim, several concentrations of perlite particles were loaded to the Ilmenite weighted drilling fluid. The tests were conducted under high-pressure high-temperature environment according to API standards. The results of the drilling fluid (containing perlite) were compared with a reference drilling fluid (zero concentration of perlite). It is observed that the perlite containing formulation has improved filtration properties. The flake-shaped perlite particles blocked the filter cake pores and accordingly produced an impermeable filter cake. There was a drastic drop in the filter cake overall permeability after adding perlite concentration of 3 lb/bbl, from 6.09 × 10−3 Darcy to 1.46 × 10−3 Darcy and a significant drop (55%) in the associated filtration volume from 18.5 cm3 to 8.5 cm3. Moreover, perlite-based filter cake lowered the pore size of the filter cake and decreased the filter cake thickness by 45%.

Computationally efficient simulation of non-isothermal two-phase flow during well construction using a new reduced drift-flux model

• A novel reduced drift-flux model for non-isothermal two-phase flow is developed. • This model considers transient heat transfer and gas-in-oil solubility behavior. • This model shows higher accuracy compared to historical reduced drift-flux models. • This model runs two orders of magnitude faster than real-time. • This model is validated using both field data and benchmark models. Two-phase flow modeling is important in well construction field for well planning and real-time applications. In this paper, a new non-isothermal two-phase flow model is presented that improves upon the simulation accuracy and capability of historical reduced drift-flux models (RDFM) while still retaining high computational efficiency. Built on the “no pressure wave” assumption of the RDFM, our new RDFM achieves improvements through calculating the temperature dynamics, considering interface mass transfer (i.e., gas-in-oil solubility behavior), and introducing a new lumped pressure dynamics model. By including these physical factors that are critical for practical applications, the proposed RDFM shows higher simulation accuracy and capability compared to historical RDFMs. The validity of the proposed model is proven by comparing it to field measurements, benchmark models, and the classical drift-flux model. Moreover, the proposed RDFM successfully retains the high computational efficiency of historical RDFMs even with the addition of the aforementioned complex physical dynamics. When conducting full-scale gas influx simulations, the proposed RDFM achieves a computational speed at more than two orders of magnitude faster than real-time. Due to its good performance on both computational efficiency and simulation accuracy, the proposed model is suitable for real-time applications in most well construction scenarios. It is especially superior to historical RDFMs when simulating more complicated but still common scenarios, e.g., deepwater wells drilled in high-pressure high-temperature environments, and wells experiencing gas-in-oil solubility behavior.

Improved High-Pressure, High-Temperature (HPHT) Materials Qualification Using Dissolved H2S Concentration as the Sour Service Scalable Metric

Gas phase H2S partial pressure (PH2S) is associated with sulfide stress cracking (SSC) and is routinely used as the “scalable” parameter to qualify materials for high-pressure, high-temperature (HPHT) wells. Candidate materials for HPHT wells routinely require ANSI/NACE MR0175/ISO 15156 compliance because a few mole ppm of H2S at high pressure may place the well beyond the 0.05 psia (0.3 kPa) sour service threshold. PH2S has been accepted historically as the scalable sour severity parameter. However, as the total pressure increases, the relationship between PH2S and the dissolved H2S concentration becomes nonlinear. This limits the robustness of PH2S as the sour severity metric. Thus, ISO 15156-1:2020 now permits the use of H2S fugacity (fH2S), H2S activity (aH2S), and H2S aqueous concentration (CH2S) as alternatives for sour testing. This recent revision is based on evidence that fH2S and CH2S each provide better correlations to SSC at elevated total pressures than PH2S. This paper will address the merits and challenges of using fH2S or CH2S to define sour severity: we argue that CH2S is a practical, experimentally verifiable approach, which can be used to validate ionic-equation of state frameworks used to characterize mildly sour HPHT environments.

Formation of diamond nanostructures from graphite using 10 W fibre laser

The high activation energy required for graphite–diamond transition limits its applicability in novel areas. To exploit fully the multifunctional properties of diamond in diverse fields, there is a necessity to explore more efficient ways for its synthesis. In this study, we have demonstrated a new approach for nanodiamonds formation by employing a commercially available low power 10 W continuous-wave fibre laser. The laser system is modulated to generate the high-pressure high temperature environment necessary for the phase conversion of graphite to diamond. The microsecond pulse duration combined with liquid confinement effect on plasma provide scope for a lower rate of supercooling, which restricts the epitaxial growth of the crystals. The sample is characterized by X-ray powder diffraction, transmission electron microscope and Raman spectroscopy, confirming the presence of different types of nanodiamonds including newly discovered n-diamond. The process offers many important advantages like scalable process, non-catalyst-based eco-friendly and cost-effective synthesis of metastable nanodiamonds. The results demonstrate the effectuality of inexpensive commercial lasers towards attaining the localized extreme environment necessary for direct phase conversion of diamond materials.

An integrated FMEA and MCDA based risk management approach to support life extension of subsea facilities in high-pressure–high-temperature (HPHT) conditions

The majority of facilities installed in offshore oil and gas fields during the 1980s and 1990s were designed to operate in ‘normal’ conditions. However, during the operational life of the fields, some new high pressure/high temperature (HPHT) wells may be discovered and tied back to older facilities. Operating these facilities beyond their design parameters in harsh environments may lead to catastrophic failures, resulting in significant economic losses and environmental problems. Managing the risks associated with failure of ageing subsea facilities in HPHT environments is considered as a very complex and critical task. To overcome such challenge, there is a need for development of decision-making methods that are capable of estimating precisely the risks associated with HPHT conditions as well as prioritising the risk mitigation and remediation strategies. This paper aims to propose an integrated risk management framework – based on Failure Mode and Effects Analysis (FMEA) approach and a hybrid Multi-Criteria Decision Analysis (MCDA) model – for evaluating the risks and prioritising mitigation strategies over the extended lifetime of subsea facilities in HPHT environments. For the purpose of illustrating the model, a case study of subsea manifold and flowlines is provided and the results are evaluated and discussed. Our findings indicate that the proposed approach offers significant improvement to the classical risk management processes applied to subsea oil and gas facilities as it can assist asset managers, risk analyst, regulators and policy makers with a decision model which considers both subjective (qualitative) judgements and objective (quantitative) evaluation measures.

Nanomaterial-Based Drilling Fluids for Exploitation of Unconventional Reservoirs: A Review

The world’s energy demand is steadily increasing where it has now become difficult for conventional hydrocarbon reservoir to meet levels of demand. Therefore, oil and gas companies are seeking novel ways to exploit and unlock the potential of unconventional resources. These resources include tight gas reservoirs, tight sandstone oil, oil and gas shales reservoirs, and high pressure high temperature (HPHT) wells. Drilling of HPHT wells and shale reservoirs has become more widespread in the global petroleum and natural gas industry. There is a current need to extend robust techniques beyond costly drilling and completion jobs, with the potential for exponential expansion. Drilling fluids and their additives are being customized in order to cater for HPHT well drilling issues. Certain conventional additives, e.g., filtrate loss additives, viscosifier additives, shale inhibitor, and shale stabilizer additives are not suitable in the HPHT environment, where they are consequently inappropriate for shale drilling. A better understanding of the selection of drilling fluids and additives for hydrocarbon water-sensitive reservoirs within HPHT environments can be achieved by identifying the challenges in conventional drilling fluids technology and their replacement with eco-friendly, cheaper, and multi-functional valuable products. In this regard, several laboratory-scale literatures have reported that nanomaterial has improved the properties of drilling fluids in the HPHT environment. This review critically evaluates nanomaterial utilization for improvement of rheological properties, filtrate loss, viscosity, and clay- and shale-inhibition at increasing temperature and pressures during the exploitation of hydrocarbons. The performance and potential of nanomaterials, which influence the nature of drilling fluid and its multi-benefits, is rarely reviewed in technical literature of water-based drilling fluid systems. Moreover, this review presented case studies of two HPHT fields and one HPHT basin, and compared their drilling fluid program for optimum selection of drilling fluid in HPHT environment.

Q Versatile Seismic Imager (QVSI) Successfully Predicts Target Depth and Pore-Pressure in HPHT Environment

Drilling in any environment is challenging as it poses a challenge to drill reservoir targets without losses and minimum casing strings and is even challenging in HPHT (high pressure high temperature) environment. Seismic is the fundamental for pre-drill prognosis and completion design. The target depth prognosis is achieved through depth transformation by using seismic velocities or available velocity logs in the nearby field or block and often has varying degree of uncertainty in target depths depending upon the suitable of the velocity function used. The velocity function used could be affected due to available seismic bandwidth or structure. These uncertainties in target depths often lead to increased well costs as a result of wellbore stability issues & undesired casing strings. Most common issue faced by drillers is the target confirmation & distance to these targets ahead of bit. Vertical seismic profile (VSP) look-ahead at intermediate depths is one of the approaches to mitigate these uncertainties and drill wells safely. VSP help confirm the presence of drilling targets & also predict the depth to top of these targets. Additionally, the predicted interval velocity is used to predict the pre-pressure for next section drilling. In South China Sea, oil & gas operators face a significant risk while drilling over-pressured formations. It is therefore imperative to know the depth to top of these high pressured formations to avoid drilling directly into it and risking the well. It is also important to know the pore-pressure and mud weight for the next section to be drilled for safe drilling & with minimum casing strings [1] [2] [3]. It is more difficult to get this information in the HPHT environment due to the lack of high temperature tools [4]. Schlumberger’s proprietary QVSI*—High pressure, high temperature VSI* (Versatile Seismic Imager) has been successfully used to predict the target depth for casing landing and pore-pressure prediction in HPHT environment. QVSI is the latest generation of VSI* Versatile Seismic Imager tools developed by Schlumberger to acquire high quality tri-axial borehole seismic data in extreme environment wells. The QVSI* tool uses the Q-Technology* singlesensor hardware and software and advanced wireline telemetry for fast digital seismic data transmission from borehole to surface. QVSI is a high-temperature, high-pressure array tool design that focuses on tri-axial vector fidelity and efficient data acquisition, extending the limits in a 4-tool configuration to 500°F (260℃) and 30 kpsi (207 MPa). In this paper, a case study is presented for Well-XX for CNOOC from South China Sea. The well-xx is located in Yanyan Sag, Qiongdongnan Basin and the downhole temperature was 204℃. The main target layer is Lingshui III sandstone, which is controlled by Northwest fault. It is a gas well and critical for the client to land the casing at right depth and know the drilling parameters for the next section ahead. QVSI* predicted the target depth within ±2 m for decision on casing point. The predicted pore pressure was within ±0.1 ppg.

Autoclave design for high pressure-high temperature corrosion studies

Purpose – The purpose of this paper is to develop an autoclave that can be used to assess corrosion behaviour of suitable material in high-pressure–high-temperature (HPHT) environments. Many new discoveries of oil and gas field are in HPHT environments. The development of such fields requires appropriate selection of materials that are able to withstand not just the service loads but also corrosive production fluids in the HPHT environment. Design/methodology/approach – The exposure of material samples to elevated pressure and temperature is usually done using an autoclave. The suitability of an existing autoclave for HPHT corrosion studies is provided together with suggestions on necessary design modifications. An alternative design of the autoclave is proposed based on functionality requirements and life cycle cost assessment. Findings – It is concluded that the existing autoclave was unsuitable for HPHT corrosion tests, and modifications were very expensive to implement and/or not foolproof. A new autoclave was designed, manufactured, tested and successfully used to study the effect of aqueous solution on the corrosion of a pipe subject to a combination of axial tension, internal pressure and elevated temperature. Research limitations/implications – The maximum design pressure of 15 MPa is more than sufficient for high-pressure corrosion studies in aqueous solution where partial pressure of the dissolved gas is one of the main controlling parameters. However, the design pressure is only suitable for corrosion studies in a seawater environment of up to 1,500 m water depth. Originality/value – A new design of autoclave together with all the necessary piping, assembly and control system is proposed for HPHT corrosion studies. The autoclave can be used as standalone or integrated with a mechanical testing machine and thus enables corrosion studies under a wide range of loading.

Broadband supercontinuum laser absorption spectrometer for multiparameter gas phase combustion diagnostics.

We report on the development and application of a broadband absorption spectrometer utilizing a pulsed supercontinuum laser light source and dispersion compensating fiber with a single-pass absorption path to obtain absolute methane mole fractions in a laminar nonpremixed CH(4)/air flame supported on a Wolfhard-Parker burner. The basic principle of supercontinuum broadband absorption spectroscopy (SCLAS) provides advantageous means of combustion diagnostics since the broad spectral coverage allows for use in high-pressure high-temperature environments. Furthermore, a previously validated tunable diode laser absorption spectroscopy fitting algorithm was applied to the recorded spectra and found to be applicable to SCLAS measurements as well, by comparison of fitted methane gas concentrations to reference measurements on the Wolfhard-Parker burner. The spectrometer reached spectral resolutions of up to 0.152 cm(-1), while providing a spectral coverage of over 110 cm(-1), with an absorption path length of only 41 mm. First measurements of absolute CH(4) mole fractions showed the suitability of SCL-based spectroscopy for combustion diagnostics with short absorption path lengths in the nIR spectral region. Here, we achieved in-flame methane mole fraction resolutions of 3%(Vol.) (1210 ppm·m) and optical resolutions of up to 1.1×10(-2). Based on this first validation, this method can now be extended to other species and combustion parameters such as temperature and pressure.

The Effects of Various Parameters on Wellbore Stability During Drilling Through Shale Formations

Field evidence indicates that the thermal and chemical regimes in wellbore considerably affect the wellbore stability. This study presents a general coupled model for transport of solute, solvent and heat including their combined effects on the wellbore stability. Optimization of drilling fluid parameters is crucial for wellbore stability analysis particularly in high pressure-high temperature environments. The coupled effects of chemical potential and temperature gradients on fluid flow significantly change the pore pressure and stress around a borehole. The effects of various parameters such as mud weight, solute concentration gradient, shale properties, and temperature gradient on wellbore stability have been investigated.

Experimental Investigation on the Influence of High Pressure and High Temperature on the Mechanical Properties of Deep Reservoir Rocks

Deep and ultra-deep resources extraction has resulted in the challenge of drilling into high-pressure, high-temperature (HPHT) environments. Drilling challenges at such extreme conditions prompted NETL to develop a specialized ultra-deep drilling simulator (UDS) for investigating drill behavior in such conditions. Using the UDS apparatus, complex laboratory tests were performed on Carthage marble (Warsaw limestone) and Crab Orchard sandstone, which represent the rocks in the basins of the Tuscaloosa trend in southern Louisiana and the Arbuckle play in Oklahoma and North Texas. Additionally, numerical models of the UDS were developed for performing parametric analyses that would be impossible with the UDS alone. Subsequently, it was found that the input properties for these two rock types at such extreme pressure and temperature conditions were unavailable. Therefore, a suite of unconfined compressive strength, indirect tensile strength, and triaxial compression tests (σ1 > σ2 = σ3) were performed on Carthage marble and Crab Orchard sandstone for investigating their behavior in HPHT environments. The HPHT experiments were performed at confining pressures ranging from atmospheric to 200 MPa, and with temperatures ranging from 25 to 180 °C. The influences of confining pressure and temperature on the mechanical properties of two rocks were investigated.

Influence of pH on Hydrogen Absorption in Duplex Stainless Steel

With rising demands, oil and gas exploration of high-pressure high-temperature (HPHT) wells are increasing worldwide. Due to aggressiveness of HPHT environments, piping and equipments are constructed with high-strength corrosion resistant alloys (CRAs). Duplex stainless steel is one of the candidate alloys that offer high strength along with corrosion resistance. It possesses the advantages of both austenitic and ferritic stainless steels and hence, the name duplex or dual phase stainless steel. In order to control corrosion, cathodic protection is commonly being employed on the structures and equipment. Cathodic protection is accomplished by applying a direct current to the structure which causes the structure potential to change from the natural corrosion potential (Ecorr). The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Hydrogen embrittlement (HE) is an associated phenomenon, which results in the production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of metals and welds. To prevent this embrittlement, cathodic protection is closely studied in terms of finding the critical potential, pH, temperature etc. that does not cause hydrogen embrittlement. This paper describes the study carried out to find the role of pH on the absorption of hydrogen in Duplex Stainless steel. It has been observed that at a critical pH, hydrogen intake in the sample is very high, as compared to the pH below and above the critical pH. Critical pH observed for duplex stainless steel is a trade of between hydrogen evolution and absorption for given duplex structure.

Retrieval of soot aggregate morphology from light scattering/extinction measurements in a high-pressure high-temperature environment

Soot aggregates have been produced in a series of experiments based on the pyrolysis of ethylene in a shock tube facility, for pressure and temperature varying, respectively, in the range ∼ 10–15 bar and ∼ 1800–2000 K. In situ light scattering/extinction coupled measurements have been performed and the process has been followed with high spatial and temporal resolution (μm/μs). On the basis of the Kumar and Tien approach for randomly oriented aggregates [Kumar and Tien (1989) Combust. Sci. Technol. 66, 199–216], we investigated the sensitivity of the angular scattering pattern and of the dissymmetry ratio for straight chain and random cluster morphologies to the refractive indices, the number and diameters of primary spheres (spherules) in the agglomerate and the solid volume fraction of the cluster. The time variation of the scattered light intensity measured at different scattering angles θ (30°, 90°, 150°) is shown to enable deduction of the prevailing morphology of the (self-organizing) aggregate. At the end of the examined agglomeration process, the resulting soot aggregates appear to be structured on average as chains of 5–10 spherules with spherule diameter of ≈ 25–30 nm.