The research and development of technical and technological solutions for the operation of oil wells with increased gas content

In the practice of oil production, there are oil deposits with high values of gas content (gas factor), from tens to hundreds of cubic meters of gas per one ton of oil produced. Gas dissolved in oil and coming from the reservoir into the well along with the liquid phase (oil, water), under certain thermodynamic conditions, is capable of forming hydrates, which complicate the operation of downhole pumping equipment, reduce the efficiency of pumps and well flow rate. The formation of gas hydrate plugs in the well requires the total overhaul, which leads to an increase in non-productive time, financial costs and an increase in lost profits on lost oil. Considered in the article technologies and devices that prevent the formation of gas hydrates in marginal wells with a high gas content in oil have shown their unreliability and low efficiency. The authors propose for the consideration a new effective technology for the operation of such wells, which makes it possible to avoid the formation of hydrates. Keywords: well; gas content; hydrates; production; oil; valve; coupling; pump.

CONDITIONS OF THE PHASE TRANSITION DURING THE FLOW OF A GAS-LIGUID MIXTURE IN CONTROLLED CHOKES

The article deals with the issues of phase transition in gas-liquid mixtures of controlled chokes. The relevance of the research topic and its scientific novelty are given. The criteria for the occurrence of cavitation and hydrate formation in liquid and gaseous fluids are presented. The equations that allow to determine the condition of the phase transition from the liquid state to the gas – liquid state the appearance of cavitation in the cross-section of the flow channel of the controlled choke are described. The article describes a modern method of protecting the design of the controlled throttle from the phenomenon of cavitation. Protection is performed by installing and using throttle cells or throttling stages. The result of the use of throttle cells is given. An example of the formation of hydrates in a gas-liquid mixture during its flow through a controlled choke is considered. The criterion and method for determining the conditions of hydrate formation in the flow channel of the controlled choke is given, which consists in constructing the operating curve of the controlled choke and its intersection with the curve of hydrate formation of the gas-liquid mixture to determine the conditions and areas of hydrate formation. The scientific novelty of the work includes the criteria for the conditions of the phase transition, as well as the provision of practical recommendations to specialists involved in the design and operation of the controlled chokes. According to its content, the article is of interest to specialists involved in the development and operation of pneumatic/hydraulic systems, and in particular, the controlled chokes.

Hydration Modification of Cement in the Presence of Diethanol-Isopropanolamine

In this investigation, calorimetry, quantitative X-ray diffraction analysis and the scanning electron microscopy were applied to explore the mechanism of hydration modification of cement with diethanol-isopropanolamine (DEIPA). It showed that the addition of DEIPA favoured the strength development on 3 and 28 days, but was undesirable for the 1d strength. The reason for this was that the dissolution of intermediate phase being promoted by DEIPA participated in the aluminate reaction interrupting the normal hydration of C3S. Appropriate adjustment on SO3 content in the cement was able to slow down the rate of aluminate reaction allowing C3S to react in a right fashion, which gave an optimum strength enhancement at early ages. The addition of DEIPA also impacted the formation of hydrates. Significant differences can be recognized in quantities, chemical compositions and the morphologies of hydrates in blank sample and the DEIPA-dosing ones. With the help of SO3 adjustment in cement with DEIPA, a great number of hydro-sulfoaluminates precipitated at the early stage of hydration to decrease the porosity of hardened cement pastes, which contributed to the strength gain of cement.

Predicting Deliquescence Relative Humidities of Crystals and Crystal Mixtures

The presence of water in the form of relative humidity (RH) may lead to deliquescence of crystalline components above a certain RH, the deliquescence RH (DRH). Knowing the DRH values is essential, e.g., for the agrochemical industry, food industry, and pharmaceutical industry to identify stability windows for their crystalline products. This work applies the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) to purely predict the DRH of single components (organic acids, sugars, artificial sweeteners, and amides) and multicomponent crystal mixtures thereof only based on aqueous solubility data of the pure components. The predicted DRH values very well agree with the experimental ones. In addition, the temperature influence on the DRH value could be successfully predicted with PC-SAFT. The DRH prediction also differentiates between formation of hydrates and anhydrates. PC-SAFT-predicted phase diagrams of hydrate-forming components illustrate the influence of additional components on the hydrate formation as a function of RH. The DRH prediction via PC-SAFT allows for the determining of the stability of crystals and crystal mixtures without the need for time-consuming experiments.

Proxy Model for Real-Time Estimation of Cool Down Time of Subsea Production System to Prevent Hydrates Formation

Objectives/Scope The benefits of real-time estimation of the cool down time of Subsea Production System (SPS) to prevent formation of hydrates are shown on a real oil and gas facility. The innovative tool developed is based on an integrated approach, which embeds a proxy model of SPS and hydrate curves, exploiting real-time field data from the Eni Digital Oil Field (eDOF, an OSIsoft PI based application developed and managed by Eni) to continuously estimate the cool down time before hydrates are formed during the shutdown. Methods, Procedures, Process The Asset value optimization and the Asset integrity of hydrocarbon production systems are complex and multi-disciplinary tasks in the oil and gas industry, due to the high number of variables and their synergy. An accurate physical model of SPS is built and, then, used to develop a proxy model, which integrates hydrate curves at different MeOH concentration, being able to estimate in real time the cool down time of SPS during the shutdown exploiting data from subsea transmitters made available by eDOF in order to prevent formation of hydrates. The tool is also integrated with a user-friendly interface, making all relevant information readily available to the operators on field. Results, Observations, Conclusions The integrated approach provides a continues estimation of cool down time based on real time field data (eDOF) in order to prevent formation of hydrates and activate preservation actions. An accurate physical model of SPS is built on a real business case using Olga software and cool down curves simulated considering different operating shutdown scenarios. Hydrate curves of the considered production fluid are also simulated at different MeOH concentration using PVTsim NOVA software. Off-line simulated curves are then implemented as numerical tables combined with eDOF data by an Eni developed fast executing proxy model to produce estimated cool down time before hydrates are formed. A graphic representation of SPS behavior and its cool down time estimation during shutdown are displayed and ready to use by the operators on field in support of the operations, saving cost and time. Novel/Additive Information The benefits of real time estimation of the cool down time of SPS to prevent hydrates formation are shown in terms of saving of time and cost during the shutdown operations on a real case application. This integrated approach allows to rely on a continue, automatic and acceptably accurate estimate of the available time before hydrates are formed in SPS, including the possibility to be further developed for cases where subsea transmitters are not available or extended to other flow assurance issues.

On liquid phase hydrates formation in pipelines in the course of gas non-stationary flow

Nowadays, when the emphasis is on alternative means of energy, natural gas is still used as an efficient and convenient fuel both in the home (for heating buildings and water, cooking, drying and lighting) and in industry together with electricity. In industrial terms, gas is one of the main sources of electricity generation in both developed and developing countries. Pipelines are the most popular means of transporting natural gas domestically and internationally. The main reasons for the constipation of gas pipelines are the formation of hydrates, freezing of water plugs, pollution, etc. It is an urgent task to take timely measures against the formation of hydrates in the pipeline. To stop gas hydrate formation in gas transporting pipelines, from existing methods the mathematical modelling with hydrodynamic method is more acceptable. In this paper the problem of prediction of possible points of hydrates origin in the main pipelines taking into consideration gas non-stationary flow and heat exchange with medium is studied. For solving the problem the system of partial differential equations governing gas non-stationary flow in main gas pipeline is investigated. The problem solution for gas adiabatic flow is presented.

Surface Charge Properties of Marble Powder and its Effect on the Formation of Hydrates in Cement Paste

Replacing part of cement with waste stone powder can reduce the use of cement, thus reducing energy consumption and CO2 emission. Different stone powders affect the properties of cement-based materials differently. It is important to clarify the effect of the surface properties of the stone powder on the properties of cement-based materials. In this paper, the charge properties of marble powder and its effect on the formation of hydrates were investigated. Zeta potential was used to study the charge properties of the marble surface. Parallelly, the morphology of hydrates on the surface of the cement and marble particles at a very early hydration age was observed by using SEM. Finally, the influence of the surface charge properties of the marble particles on the formation of hydration products of cement was discussed. The results showed that the marble particles have specific adsorption of Ca2+ (chemical adsorption). Therefore, the marble particles in the simulated solution can adsorb a large amount of Ca2+, thus achieving a high potential value and facilitating the formation of hydrates on their surface. However, the adsorption of Ca2+ towards the surface of the cement particle is driven by a relatively weak electrostatic force. Compared with the marble particles, less Ca2+ ions are adsorbed, and thus, fewer hydrates are formed on the surface of cement particles.

Methane Hydrate Formation and Dissociation in Sand Media: Effect of Water Saturation, Gas Flowrate and Particle Size

Assessing the influence of key parameters governing the formation of hydrates and determining the capacity of the latter to store gaseous molecules is needed to improve our understanding of the role of natural gas hydrates in the oceanic methane cycle. Such knowledge will also support the development of new industrial processes and technologies such as those related to thermal energy storage. In this study, high-pressure laboratory methane hydrate formation and dissociation experiments were carried out in a sandy matrix at a temperature around 276.65 K. Methane was continuously injected at constant flowrate to allow hydrate formation over the course of the injection step. The influence of water saturation, methane injection flowrate and particle size on hydrate formation kinetics and methane storage capacity were investigated. Six water saturations (10.8%, 21.6%, 33%, 43.9%, 55% and 66.3%), three gas flowrates (29, 58 and 78 mLn·min−1) and three classes of particle size (80–140, 315–450 and 80–450 µm) were tested, and the resulting data were tabulated. Overall, the measured induction time obtained at 53–57% water saturation has an average value of 58 ± 14 min minutes with clear discrepancies that express the stochastic nature of hydrate nucleation, and/or results from the heterogeneity in the porosity and permeability fields of the sandy core due to heterogeneous particles. Besides, the results emphasize a clear link between the gas injection flowrate and the induction time whatever the particle size and water saturation. An increase in the gas flowrate from 29 to 78 mLn·min−1 is accompanied by a decrease in the induction time up to ~100 min (i.e., ~77% decrease). However, such clear behaviour is less conspicuous when varying either the particle size or the water saturation. Likewise, the volume of hydrate-bound methane increases with increasing water saturation. This study showed that water is not totally converted into hydrates and most of the calculated conversion ratios are around 74–84%, with the lowest value of 49.5% conversion at 54% of water saturation and the highest values of 97.8% for the lowest water saturation (10.8%). Comparison with similar experiments in the literature is also carried out herein.

Ultra-Rapid Uptake and Highly Stable Storage of Methane as Combustible Ice

<p>The continuously increasing trend of natural gas (NG) consumption due to its clean nature and abundant availability indicates an inevitable transition to an NG-dominated economy. Solidified natural gas (SNG) storage via combustible ice or clathrate hydrates presents an economically sound prospect, promising high volume density and long-term storage. Herein, we establish 1,3-dioxolane (DIOX) as a highly efficient dual-action (thermodynamic and kinetic promoter) additive for the formation of clathrate (methane sII) hydrate. By synergistically combining a small concentration (300 ppm) of the kinetic promoter L-tryptophan with DIOX, we further demonstrated the ultra-rapid formation of hydrates with a methane uptake of 83.81 (0.77) volume of gas/volume of hydrate (v/v) within 15 min. To the best of our knowledge, this is the fastest reaction time reported to date for sII hydrates related to SNG technology and represents a 147% increase in the hydrate formation rate compared to the standard water–DIOX system. Mixed methane–DIOX hydrates in pelletized form also exhibited incredible stability when stored at atmospheric pressure and moderate temperature of 268.15 K, thereby showcasing the potential to be industrially applicable for the development of a large-scale NG storage system.</p>