High-pressure Oil Research Articles

Dynamic solution of high pressure tubing

In the real environment, the pressure of high-pressure oil pipe is not always stable due to the process of oil in and out. We created a simulation experiment: to set the time for each opening of the one-way valve to change the pressure in the high-pressure tubing, ensuring that the pressure remains relatively stable under the initial pressure condition 100Mpa. By using the simulated conditions, we obtained the relationship between elastic modulus E and pressure P with high fitting degree, and deduced the relationship between pressure P and density temperature. Since the tubing size V is constant, we established the approximate dynamic balance model of fuel mass in high pressure tubing according to the mV mass. Since the opening time of the one-way valve is unknown, the simplified operation method is used to find the approximate solution and then the dichotomy method is used to find the results in this range. Our contribution is that we proposed a method to control the pressure steadily and rapidly in simulation. For each search result, the iterative method is used to obtain the mean pressure of the injection pipe after the pressure is stable, and the objective function is established to make the average pressure reach 150Mpa. Finally, we present the exact solution with MATLAB simulation.

Nonlinear flow-induced vibration response characteristics of a tubing string in HPHT oil&gas well

This study has established a nonlinear flow-induced vibration (FIV) model of tubing string by using the micro-element method and energy method with the Hamiltonian variational principle, in order to address the vibration failure problem of the tubing string induced by high-speed fluid flow in the tubing of high temperature and high pressure (HPHT) oil&gas well. This model considered factors such as borehole trajectory changes, wellbore temperature and pressure variations, self-weight of the tubing string, and the contact-impact of the tubing-casing. Based on the structural parameters of the M high-yield gas well in the South China Sea, a simulation experiment of the tubing string vibration was conducted according to the similarity principle. A comparison between the experiment data and theoretical data showed that the calculation accuracy exceeded 84%, which verified the correctness and validity of the nonlinear vibration model established in this study. On this basis, the influence of the production rate, well inclination angle, well section length, and packer position on the vibration response characteristics of the tubing string were analyzed systematically. It was found that: ①with the increase of the production rate, the vibration response of the tubing string became clearer. The production rate interval that showed abrupt changes was from 0.9 ~1.2 million m3/day. Thus, during designing, such production rate intervals with abrupt changes should be avoided to ensure the safe usage of the tubing strings; ②with the increase of the well inclination angle, the vibration response of the tubing string decreased to a certain extent. Regarding the influence of the well section length, the longitudinal vibration response of the tubing string was most sensitive to the length of the vertical section, followed by the steady inclined section, and finally the angle building section. Thus, during designing, the length of the vertical section should be reduced, while the length of the angle building section and the well inclination angle of the steady inclined section should be increased; ③As the position of the production packer moved up, the vibration responses of the lower and middle tubing strings both decreased, and the optimal packer position was between 3,549 and 3,666 m. The research results can serve as an effective analysis tool and provide a theoretical basis for the safety design of the tubing strings in the HPHT oil&gas well site.

A review in nanopolymers for drilling fluids applications

Continued economic growth leads to considerably increase energy demand produced from oil and gas. It's fact that conventional hydrocarbon reserves are nowadays at the depletion stage while unconventional reserves exhibits difficulties in drilling process due hazardous conditions of high pressure and high temperature (HPHT), thus it is necessary to use drilling fluids of high performance. Drilling operation is inextricably associated with the use of drilling fluids/muds while successful and safe drilling operations are depended on the efficiency of the drilling fluid that is used. Engineering in high temperature and high pressure oil or gas wells is a challenging task where the contribution of chemistry of synthetic polymer is of high significance. Although, compared to conventional muds, polymer drilling systems demonstrate enhanced rheological properties, nonetheless at HPHT conditions they may arise some stability problems due to inappropriate chemical and physical properties as well as mechanical and thermal properties that polymers exhibit. Application of nanotechnology provides innovative materials which can boost drilling technology and restrain technical and environmental issues to drill unconventional hydrocarbons reservoirs. Rheological performance of environmental friendly water based (WBM) drilling fluids can be enhanced with the use of nanofluids as well as filtrate loss volume reduction and improvement of shale inhibition characteristic. This article collects information about using polymers and nanopolymers for oil and gas drilling technology.

The drill stem testing of a high-pressure santos basin pre-salt oil well: guidelines for well design, operation description, and prior learned lessons

The drill stem testing of a high-pressure santos basin pre-salt oil well: guidelines for well design, operation description, and prior learned lessons

Pressure Control of High Pressure Tubing Based on Fluid Mechanics

This paper studies the problem of the constant pressure control for high pressure tubing. The main factors affecting the pressure change in high pressure oil pipe are the opening time of check valve and the cam angular velocity. Based on the theory of fluid mechanics, ordinary differential equation and Fourier series, the flow-pressure model and pressure-cam angular velocity model are established, respectively. Furthermore, the above model is extended to the case of multiple nozzles. These three models accurately express the functional relationship between the fuel flow rate, the pressure in the tubing and the cam angular velocity. According to the established models, the pressure in the high-pressure oil pipe can be accurately controlled by adjusting some parameters. Finally, a simulation example is given to verify the effectiveness of the proposed method.

Evaluation of polymer/bentonite synergy on the properties of aqueous drilling fluids for high-temperature and high-pressure oil wells

The increasing demand for energy sources has led to oil field exploration under inhospitable conditions, where non-aqueous drilling fluids are commonly used due their physical and chemical stability. However, they exhibit a number of environmental constraints and the cuttings produced require expensive treatments before disposal. Aqueous drilling fluids are currently less thermally resistant and generally entail the use of chromium lignosulfonate as clay dispersant, which provides stability to rheological properties and filtration control under high temperature and high pressure (HTHP). This study elucidates the role played by synergic effect of a novel eco-friendly high-performance water-based drilling fluid using bentonite and vinyl polymers (polyvinylpyrrolidone (PVP) and partially hydrolyzed polyacrylamide (PHPA)) as the main constituents. Filtration and rheological properties of the drilling fluids were determined on a HTHP filtration system and on a rotational viscometer, respectively. Systems using high molar mass PVP (HMM PVP) showed higher values for viscosity, gel strength and yield stress, due to promotion of flocculation. On the other hand, dispersed systems were obtained using low molar mass PVP (LMM PVP), through ion-dipole interactions between PVP and clay particles. Dispersed systems provided stable rheological parameters over the entire range of temperature and pressure studied (up to around 120 °C and 3450 kPa). Linear clay swelling tests showed that LMM PVP and water had similar profiles, promoting clay dispersion. Profitable low filtrate volumes (12 mL) were obtained for PVP-based drilling fluids in conditions where non-aqueous fluids are currently applied.

Pressure control strategy for high-pressure tubing

The entry and ejection of fuel into and out of high-pressure oil tube are the basis of many fuel engines. However, the intermittent working process of fuel entering and exiting will be leading to pressure changes in high-pressure oil tube. Furthermore, it will affect the efficiency of an engine. Therefore, it can be seen important to control high-pressure oil tube effectively. Also, it will be increasing the efficiency of an engine, while having a greatly impact on the development of engine manufacturing and energy industry. This paper is to focus on solving pressure control under high-pressure oil tube. The problems are stable pressure at the inlet of the high-pressure tubing and high-pressure oil tube with no pressure reducing valve and only one nozzle. Regarding the first one, we used the least square method to fit an elastic modulus and pressure data. Then, a differential equation model of pressure and time were set inside high-pressure oil tube. Meanwhile, we also worked on a delayed injection strategy and traversal search algorithm to have results. So, the optimal delayed injection time is 0.23 ms while the one-way valve opening time is 3.06 ms . The maximum offset pressure is about0.3 MPa. The second case which is based on the first case. In order to achieve pressure control, linking the pressure at the inlet of high-pressure oil tube to a cam and using the principle of mass conservation. So, it is stated that the pressure can be stabilized as much as possible when the angular velocity is 0.0275 rad/ms. Finally, we verified the feasibility of the model through simulation analysis.

Pressure Control of High-Pressure Oil Pipe

In this paper, to realize the pressure stability control of high-pressure oil pipe, the dynamic differential equation of fuel oil inlet and outlet is established based on the theory of mass conservation. According to the change of the pressure in the high-pressure tubing, an optimization model is established to achieve precise control of the working time of each part of the high-pressure oil pipe.

The Pressure Control of High-Pressure Tubing Based on Difference Equation

The situation where fuel enters and exits the high-pressure tubing is one of the important factors that affect the working efficiency of the engine. Based on the simplified high-pressure tubing model, this paper studies the control problems of high-pressure tubing injection and fuel supply under certain circumstances. According to the idea of the difference equation, the paper obtains the opening time of the one-way valve when the pressure value of the high-pressure tubing is kept constant or rises to a specific value by enumerating the opening time of the one-way valve. By establishing the physical model of the high-pressure tubing and the fuel injection nozzle, and then using the enumeration method, the angular velocity of the high-pressure oil pump cam when the pressure of the high-pressure fuel pipe is kept constant can be obtained. Under the more complicated injector model, the control method of the injector is solved by the double enumeration method. The results show that the above model can quickly calculate the optimal working time of the high-pressure fuel pump and needle valve when the accuracy meets the requirements.

Fuel system control design based on mass conservation

Fuel entering and ejecting high-pressure fuel pipe is the basis of fuel engine operation. The intermittent operation of high-pressure oil pump and injector will lead to the change of pressure in high-pressure oil pipe. This paper studies the influence of the opening and closing of one-way value and the speed of cam angle on the pressure in high-pressure oil pipe. Because the fuel flow is unstable in the high-pressure fuel pipe, it is necessary to determine the influence of pressure change on fuel density, and then calculate the mass of fuel supply and fuel injection in unit time. Considering the principle of mass conservation, the problem can be transformed into the length of single opening time of one-way valve when the mass of fuel entering and leaving the high-pressure oil pipe is equal in unit time interval. At the same time, by deducing the influence of the single opening time of the one-way value on the pressure in the high-pressure oil pipe, the single opening time of the one-way valve when the pressure of the high-pressure oil pipe reaches equilibrium after 2s, 5s and 10s is 0.610895ms, 0.425998ms and 0.373376ms respectively. Consider the working principle of the fuel system on the basis of the above considerations. Fit the function relationship between the needle lift and working time, deduce the change rule of flow volume of injector with time, and calculate the volume and mass of fuel injected by the injector in the working cycle. The results show that the high-pressure oil pump supplies oil 94 times in a working cycle of the injector, and the time required for the cam to rotate for one circle is 1.064ms, and the angular velocity of the cam is 5.906rad/ms. In this paper, based on the theory of unsteady liquid motion, mass conservation and energy conservation of fluid mechanics, many elements involved in the problem stem are analysed and related, and the control model of one-way valve switch and cam angular velocity is given.

Research on Pressure Controls of High Pressure Tubing Based on Simulation Model

High pressure oil pipeline is the basic component of many fuel engines, and it has great application and development value in transportation, aerospace and other national defense military. This paper examines ways to control the pressure change in the high pressure tubing under the condition of intermittent fuel entry and ejection. On the basis of determining the balance equation of each part of the injection system, this paper presents different design schemes of the high pressure fuel system under different operating parameters of the high pressure tubing by establishing the simulation model.

Effect of Cam Angular Velocity on Working Efficiency of Fuel Engine

The intermittent working process of fuel entry and injection will cause the pressure in the high-pressure fuel pipe to change, causing deviations in the amount of injected fuel, which will affect the engine’s operating efficiency. Taking a high pressure oil pump system as an example, the feasibility of using constant pressure to improve the working efficiency of the high pressure fuel system is studied. First, a series of simplified assumptions are made for the model. Secondly, use MATLAB software to make cam mechanism diagram. A cam angular velocity model based on pressure stability was established using the fuel quality of one injection of the injector and the fuel quality of one cam rotation. Calculate the number of times the cam needs to rotate to get the time that the cam needs to rotate once, so as to determine the high stability of the cam. The angular velocity required for tubing pressure was obtained.

Microscopic Pore Structure of Surrounding Rock for Underground Strategic Petroleum Reserve (SPR) Caverns in Bedded Rock Salt

Using salt caverns for an underground strategic petroleum reserve (SPR) is considered as an ideal approach due to the excellent characteristics of low porosity, low permeability, self-healing of damage, and strong plastic deformation ability of rock salt. Salt deposits in China are mostly layered rock salt structures, with the characteristics of many interlayers, bringing great challenges for the construction of SPR facilities. Studying the microscopic pore characteristics of the rock surrounding SPR salt caverns in different environments (with brine and crude oil erosion) is necessary because the essence of mechanical and permeability characteristics is the macroscopic embodiment of the microscopic pore structure. In this paper, XRD tests and SEM tests are carried out to determine the physical properties of storage media and surrounding rock. Gas adsorption tests and mercury intrusion tests are carried out to analyze the microscopic pore structure, specific surface area variation and total aperture distribution characteristics of SPR salt cavern host rock. Results show that: (1) Large numbers of cores in interlayer and caprock may provide favorable channels for the leakage of high-pressure crude oil and brine. (2) The blockage of pores by macromolecular organic matter (colloid and asphaltene) in crude oil will not significantly change the structural characteristics of the rock skeleton, which is beneficial to the long-term operation of the SPR salt cavern. (3) The water–rock interaction will bring obvious changes in the micro-pore structure of rock and increase the leakage risk of the storage medium. The results can provide theoretical bases and methods for the tightness analysis of China’s first underground SPR salt cavern.

Combined effects of high hydrostatic pressure and dispersed oil on the metabolism and the mortality of turbot hepatocytes (Scophthalmus maximus)

Since the DeepWater Horizon oil spill and the use at 1450 m depth of dispersant as a technical response, the need of relevant ecotoxicological data on deep-sea ecosystems becomes crucial. In this context, this study focused on the effect of high hydrostatic pressure (10.1 MPa) on turbot hepatocytes isolated from fish exposed either to chemically dispersed oil, mechanically dispersed oil or dispersant alone. Potential combined effects of oil/dispersant and hydrostatic pressure, were assessed on cell mortality (total cell death, necrosis and apoptosis), cell viability and on hepatocyte oxygen consumption (MO2). No change in cell mortality was observed in any of the experimental conditions, whereas, the results of cell viability showed a strong and significant increase in the two oil groups independently of the pressure exposure. Finally, oil exposure and hydrostatic pressure have additive effects on oxygen consumption at a cellular level. Presence of dispersant prevent any MO2 increase in our experimental conditions. These mechanistic effects leading to this increased energetic demand and its eventual inhibition by dispersant must be investigated in further experiments.

Secondary surface modified laponite-based nanocomposite hydrogel for gas shutoff in wellbore

During the exploration and development of high temperature and high-pressure oil and gas resources, high-pressure gas intrusion into the wellbore creates a significant challenge to the well drilling and completion. Polymer gel is a useful tool for gas invasion delay in the wellbore. This paper describes a novel laponite-based nanocomposite gel plug that involves a new method of secondary modification of the laponite structure to decrease the gelation rate at high temperatures. The secondary surface-modified laponite controls the gelation rate better at the high-temperature of 160 °C. The secondary surface-modified laponite-based nanocomposite gel (LPGEL) is formulated using 0.1% potassium pyrophosphate (TKPP), 0.03% thiourea, 3% laponite, 1.2%–2% sulfonated polyacrylamide (SPAM), and 0.4%–0.8% solutions of the cationic organic crosslinking agent cross-linked polyethylenimine (CPEI), which modified the surface of the laponite by changing the surface charge of the laponite particles during the crosslinking reaction. The main application properties of the LPGEL plug such as rheological behavior, thermal stability and stress-strain performance were investigated. The morphology and structure of the LPGEL plug were characterized by scanning electron microscopy (SEM) and FT-IR Fourier transform infrared spectrometry. A physical simulation was conducted to test the gas invasion delay performance for a 14 cm long LPGEL plug in fractured cores with fracture widths of 0.8 mm and 1.52 mm. Result shows that the stable gas outlet rate is 0.5–5 mL/min, dramatically delaying the gas intrusion rate. The elastic deformation capacity of LPGEL plug is an important factor to affect gas shutoff performance. The novel nanocomposite hydrogel has the potential to be served as the plugging agent in wellbore for safety control during well drilling and completion.

Laboratory experiment and field application of high pressure and high quality steam flooding

Steam flooding is an effective way to improve oil recovery after steam huff and puff for heavy oil reservoirs. The typical screening criteria for steam flooding requires reservoir pressure to be less than 5 MPa, the steam quality of conventional steam flooding in bottom hole is about 30%, heavy oil reservoir in Shengli Oilfield with character of deep burial depth, active edge and bottom water and high formation pressure (7–8 MPa), the increase of oil recovery using conventional steam flooding is not obvious, Therefore, the formation and development of steam chamber during steam flooding are studied by indoor physical simulation experiments, the feasibility of high-quality steam flooding under high pressure is analyzed. The experimental results show that the quality of steam injection has obvious influence on the expansion of steam chamber. As the steam quality increases under high pressure, the specific volume of underground steam increases, the formation time of steam chamber is shortened, the expansion distance of steam chamber increases, the effective steam flooding time is prolonged, and recovery rate improves obviously. Field tests of high-quality steam flooding under high pressure were carried out in Gudao Zhongerbei heavy oil reservoir of Shengli Oilfield, the result shows that the bottom-hole steam quality of steam injection wells is 50% and above (20% higher than conventional steam flooding), the steam chamber was effectively expanded and the performance of producing rate for production wells improves obviously. The recovery rate of the test area reached 52.1%, which was 16.8% higher than that of steam huff and puff. High-quality steam flooding technology was an effective way to improve the recovery rate of high-pressure heavy oil reservoirs.

Difficulties and Technical System in the Field of High Temperature and High Pressure

The field of high temperature and high pressure is a key area of oil and gas exploration and development in China in the future, and it is also a very rich area of oil and gas resources. Unlike conventional oil and gas fields, high-temperature and high-pressure oil and gas fields are characterized by high-pressure systems, overlapping sand bodies and more complex gas-water modes. How to effectively predict the pressure, clear the distribution of sand and water, guide the smooth implementation of drilling operations, reasonable development plan is a key step. The authors analyze the reservoir in detail from pre-drilling pressure modeling technique, reservoir fluid fine identification and reservoir formation mechanism respectively. Finally, the Dongfang M gas field has a good effect after drilling, and the output and production capacity are all over expectations, especially for the development effect of low permeability breaking the ceiling of traditional low permeability reservoir development, and form a high temperature and high pressure implementation technology system to guide the subsequent development of similar areas.

基于质量守恒的高压油管压力控制问题研究

基于质量守恒的高压油管压力控制问题研究

DYNAMICS OF THE PRESSURE FIELD DURING ISOTHERMAL FLUID MOVEMENT IN PIPES

Background The classic work of N.E. Zhukovsky on hydraulic shock in water pipes was the beginning of a large Number of studies on pressure unsteady fluid movement. The large scale of construction of a network of high-pressure oil and gas pipelines was the impetus for setting the problems of unsteady traffic. In these tasks, you have to take into account the viscosity and compressibility of the liquid, as well as hydraulic resistance. Aims and Objectives In this paper, which is mainly intended for practical purposes, we consider the problem of the fluid pressure field in round pipes under the linearized law of friction. Results It is shown how a system of equations can be transformed into a single hyperbolic equation with respect to pressure, mass velocity, or velocity for a drop of liquid. The resulting equation is a special case of the well-known Telegraph equation. This establishes an analogy between the flow of liquid or gas in pipes and the distribution of electric current along the cable. As a specific problem, the solution of the equation describing the pressure under boundary conditions of the 1st kind is obtained, i.e. the pressures at the boundaries of the pipeline section under consideration are set. Using standard substitution, inhomogeneous boundary conditions are reduced to homogeneous ones. Calculations have shown that pressure fluctuations along the length of the pipeline occur only in the start-up mode. This period depends on many factors, but the main ones are the coefficient of hydraulic resistance and the flow rate.

Crosspoint Localization of Spiral and Girth Welds of Spiral Steel Pipelines

Crosspoint of spiral and girth welds of spiral steel pipelines transporting high-pressure oil and gas is easy to crack due to welding defects and corrosion, so routine excavation and careful inspection are required. In order to reduce the workload and cost of excavation, it is necessary to determine the crosspoint's angular position on the girth weld. This article proposes a low-cost and high-efficiency method for locating the spiral-girth weld crosspoint based on the inner Spherical Detector (SD). Theoretical analysis and experiments demonstrate that the magnetometer with a smaller lift-off could detect more noticeable magnetic valley of the spiral welds at the pipe bottom, so a smaller SD should be used; the spiral direction can be determined by the phase difference of the dual-channel magnetic signals, when dual magnetometers are symmetrically fixed about the median vertical plane on the rotation axis of the SD. When the girth weld, at least one spiral weld and the spiral direction are detected and determined, the crosspoint's angular position can be calculated. The maximum localization error of the crosspoint is less than 30° and the average error is less than 20°, that is, no more than one hour's angle, whose accuracy is sufficient for excavation and maintenance in the field, because it will reduce the amount of excavation by nearly half.