Gupta, M K (Oil and Natural Gas Corporation Ltd) | Sukanandan, J N (Oil and Natural Gas Corporation Ltd) | Singh, V K (Oil and Natural Gas Corporation Ltd) | Pawar, A S (Oil and Natural Gas Corporation Ltd) | Deuri, BUDHIN (Oil and Natural Gas Corporation Ltd)
In an offshore field, mitigation of H2S from natural gas itself is a big challenge. A situation where high H2S present in well fluid increases the challenges several fold to sweet both processed oil and gas. In a wellhead platform/remote location where manual intervention requirement is minimal, conventional process has several limitation such as space availability, load on structure, frequent monitoring etc., hence may not be suitable for mitigation of H2S from processed gas and oil.
In this work, an approach is adopted for sweetening of sour gas and sour crude in an optimum way, keeping offshore constraints in mind and without usage of rotating equipment's. An integrated simulation model is developed in Aspen HYSYS process simulator wherein well fluid from well manifold is processed in three phase oil and gas separator. The gas liberated from the separator is first sweetened in adsorption columns considering three bed systems unlike general usage of two. The oil is sweetened in an envisaged stripper column utilizing sweet gas from adsorption column as stripping gas. In this work, a three bed adsorption column is envisaged wherein 1st two column in used for sweetening of gas liberated from separator which consists of around 7500ppm H2S. Sour oil from the separator which contains around 2000 ppm of dissolved H2S is processed in a stripper column for mitigation of H2S dissolved in the oil. Sweet gas liberated from 1st two column of adsorber bed is used as stripping gas for oil sweetening. H2S liberated from stripper column is routed to the 3rd column for sweetening. After this gas from all the adsorber column is combined and routed to process platform along with the sweet oil. Analysis reveals that, this scheme can sweeten altogether both oil and gas to the desired H2S level without the need of any rotating equipment's and must be a suitable for remote location.
A holistic approach was taken for sweetening of oil and gas without the need of any rotating equipment's, & any chemicals, unlike the conventional method and hence can be suitably adopted for an offshore environment or at remote location where requirement of manual intervention is bare minimum.
Foaming in absorber column for sour gas treatment using amine is a common problem which adversely affects column performance leading to reduction in sales and fuel-gas production and solvent loss. Mostly antifoam injection has been a common method to counter the foaming, large dosage and frequent dosing of antifoam many a times aggravates the problem. This study details an alternative technique based on pressure pulse mechanism to control foaming in one of ONGC's gas sweetening plants.
One of ONGC's amine based sour gas sweetening plants faced severe foaming problem frequently. The feed rate is 200 kscm/hr and absorber column operating pressure is 51 kg/cm2. The experiment utilizes the property of surface tension which fluctuates with change in pressure of the system leading to foam collapse. The experimental procedure involved varying the sour gas feed rate, thereby creating pressure pulse inside the absorber column. Differential pressure across the column which is an indicator of foaming tendency is then monitored and controlled within 1.0 kg/cm2 and recorded for establishing effectiveness of the method.
It is observed that by providing a number of cycles of pressure pulse in the absorber, the differential pressure stabilizes gradually which indicates collapse of foam. It shows that whenever there is increase in feed, expansion of bubble takes place which provides high interfacial liquid-vapour contact. On the other hand whenever there is decrease in feed rate, compression of bubble takes place which provides low interfacial liquid-vapour contact. Surface layer surrounding the bubbles in a foam acts as a membrane or skin that can stretch or relax in response to change in pressure and gives a mechanical shock which breaks the bubble. The increase of size ultimately leads to instability and break-up of the upper surface and releases the liquid holdup. Hence by using feed rate spikes, the pressure of the bubble is pulsed to higher levels and returned to substantially the original level. This cycle continues for a selected number of times so that this pressure pulse travels through the liquid and bubbles and affects its surface tension. This results into a transition phase which in very high energy level breaks the bubble and releases the gas and decreases the liquid hold up and controls the foaming phenomenon.
This paper will gives an insight into a novel methodology of mitigating foaming problem in a sour gas treating absorber just by varying the feed rates in a controlled manner. This technique eliminates the need for injecting antifoam agents which in turn will reduce the operating expenditure of the plant. Adverse impact on environment due to excessive use of antifoam agent is also minimized.
Drilling operations are faced with conditions of subsurface uncertainty with unexpected drilling hazard potential. Operation is done in 24 hours a day continuously, until drilling is declared complete. The consequence of this work environment is the potential for high work accident, one of which is caused by situational conditions in the field that allow the communication limitations in clear and detailed.
Such conditions may include high-noise working conditions, limited visibility due to weather hazards (rain, fog, dark / night), and sour gas exposure. In this condition, often verbal communication is followed by non verbal communication, either in the form of the use of horns (morse), flag raising (semaphore) and limb movements. Non-verbal communication will be more urgent if the drilling operation conditions in emergency conditions, such as the occurrence of kick, blowout and exposure to sour gases. Non-verbal communication occasionally used in any drilling site does not have standardization, thus increasing the potential for communication errors.
Methods Non-verbal instructions intended in this paper is a sign language that serves as a medium for delivering work orders (instructions). This non verbal instruction uses one limb, represented by at least 2 limb movements in at least 2 stages of movement, to interpret a command or work instruction. If less than 2 movements or less than 1 stage of movement, then the movement of the body may have meaning, but can not be implemented because the instructions are not complete
With the invention, paper and efforts of this standardization, the communication process and the delivery of orders in both normal and emergency conditions at the drilling sites can be carried out in a structured, standardized, clear, detailed and widely applicable manner. The instruction method in the form of non-verbal codes is named: NS Blind Code Drilling, which has been registered since December 2014 to the Directorate General of Intellectual Property Rights and is in process related to the patent application.
Patel, Niley (Scaled Solutions LLC) | Rafferty, Andrew (Scaled Solutions Ltd) | Stewart-Liddon, Christine (Scaled Solutions Ltd) | Hammonds, Paul (Scaled Solutions Ltd) | Graham, Gordon M. (Scaled Solutions Ltd) | Maskell, Phillip (Scaled Solutions Ltd) | Frigo, Dario M. (Plinius Chemical Consulting)
A technique has been developed to allow for the comparison of scavenging rates and scavenging capacity of different hydrogen sulphide scavengers by continuously measuring the hydrogen sulphide concentration in the gas phase of a multiphase system. In addition, the stability of the scavenger reaction products has also been investigated.
The methodology to assess the performance of the hydrogen sulphide scavenger is described. The scavenging rates of the hydrogen sulphide scavenger are compared by the contact time required to reduce the initial hydrogen sulphide concentration to a pre-determined value. In addition, the scavenging capacity of the scavengers can be calculated by recording the gaseous hydrogen sulphide concentration once the reaction has been allowed to run to completion. Finally, the stability of the scavengers and their reaction products, including carbon disulphide, are determined by treating a solution of the scavenger with excess hydrogen sulphide.
It is known that hydrogen sulphide scavengers have the potential to form reaction products that can foul the refining process. More recently, it has been identified that carbon disulphide may be produced during the scavenging reaction of some commonly used triazine based chemistries, driving a desire to identify alternative products. These works describe a new method which is capable of differentiating between the hydrogen sulfide scavenging performance of different chemistries. It also allowed for the scavengers to be differentiated with respect to the formation of both solid and oil soluble by-products, with the presence / increase in carbon disulphide analysed by gas chromatography. By doing this, the method allows for improved scavenger selection on the basis of performance, compatibility and cost.
This work presents a novel method for the assessment of relative reaction rates and scavenging capacity of hydrogen sulphide scavengers. In doing so, it allows the evaluation of cost performance and suitability of different treatments and scavenger chemistries to be evaluated. Additionally, the likelihood of a scavenger chemistry fouling the refining process due to the production of reaction by-products can be investigated.
Junwen, Wu (Sinopec Research Institute of Petroleum Exploration and Development) | Wenfeng, Jia (Sinopec Research Institute of Petroleum Engineering) | Rusheng, Zhang (Sinopec Research Institute of Petroleum Exploration and Development) | Xueqi, Cen (Sinopec Research Institute of Petroleum Exploration and Development) | Haibo, Wang (Sinopec Research Institute of Petroleum Exploration and Development) | Jun, Niu (Sinopec Research Institute of Petroleum Exploration and Development)
The high efficient foam unloading agent was developed to solve the problem of unloading of liquid loading gas well with high gas temperature, salinity and high concentration of H2S gas and gas condensate. The Gemini anionic surfactant with special comb structure was synthesized as foaming agent molecule, the modified nanoparticles with certain size and degree of hydrophobicity was adopted as solid foam stabilizer, and the fluorocarbon surfactant was designed and synthesised as gas condensate resistance components. The indoor experiment results show that the foam unloading agent showed good foaming and foam stabilizing ability when the temperature is as high as 150°C, salinity is up to 250000 ppm and H2S concentration up to 2000 ppm. Besides, the foam unloading agent present good liquid carrying ability when the volume fraction of gas condensate is as high as 50%. The field test of this foam unloading agent in Longfengshan north 201-XY well shows that, the average gas production increased from 7256 m3/day to 11329 m3/day, increased by 56%, the average differential pressure between tubing and casing dropped from 2.66 MPa to 2.38 MPa, fell by 10.5%, both liquid yield and gas production are obvious, which prove that the foam unloading agent can meet the demand of drainage gas recovery for high content gas condensate gas field.
Viscoelastic surfactants (VES) are essential components in self-diverting acid systems. Their low thermal stability limits their application at elevated temperatures. The industry introduced new VES chemistries with modified hydrophilic functional groups, which enhances their thermal stability. These new chemistries are still challenged by the lack of compatibility with corrosion inhibitors (CI). This work aims to study the nature and the mechanism of the interaction between the VES and the corrosion inhibitors, which affects both the rheological and corrosion inhibition characteristics of the self-diverting acid system.
This study is based on rheology and corrosion inhibition tests, where combinations of VES and corrosion inhibitors are tested and complemented with chemical and microscopic analysis. Negatively charged thiourea and positively charged quaternary ammonium corrosion inhibitors were selected to study their impact on both cationic and zwitterionic VES systems. Each mixture of the corrosion inhibitor and the VES was blended in a 15 and 20 wt% HCl acid mixture, then assessed for its viscosity at different shear rates, CI concentrations, and temperatures up to 280°F in live and spent acid conditions. Each acid solution was assessed using Fourier-Transform-Infra-Red (FTIR) before and after each rheology and corrosion test to track the changes of the mixture functional groups. Each mixture was examined under a polarizing microscope to assess its colloidal nature. The corrosion inhibition effectiveness of selected acid mixtures was evaluated. N-80 steel coupons were immersed statically in the acid mixture for 6 hours at 150°F and 1,000 psi. The corrosion rate was evaluated by using metal coupon weight loss analysis followed by optical microscope examination for the metal surface.
The interaction between the CI and the VES surface charges and molecular geometries dictates both the rheological and the inhibitive properties of the acid mixtures. The use of a small molecular structure anionic CI with a cationic VES, results in a fine monodispersed CI particles in the VES-acid system. The opposite charges between the CI and the VES results in electrostatic attraction forces. Both the fine dispersion and the electrostatic attraction enhances the rheological performance of the mixture and packs the corrosion-inhibiting layer. The addition of a bulk and similarly charged CI with the VES results in a coarse polydispersed CI particles with repulsive nature with the VES. These properties increase the shear-induced structures and lower the packing of the inhibition layer deposited on the metal coupons, which decrease the rheological performance of the acid mixture and increase its corrosion rate. The FTIR analysis shows that there is no chemical reaction between the CIs and the VESs tested.
This work investigates the interactions between the corrosion inhibitors and the viscoelastic surfactants. It explains the impact of the surface charge of both corrosion inhibitors and VES on their rheological and corrosion inhibition characteristics. It adds a selection criterion for compatible VES and corrosion inhibitors.
A new method has been developed to differentiate and quantify the amount of primary amines through a simple chemical process. Colored cyclic adduct compounds are formed by reaction of selective chemicals with primary amine. This adduct formation is preferential to the primary amine, even in the presence of a mixture of secondary and tertiary amines. The adduct shows selective enhanced fluorescence emission at 475-nm wavelength under specific excitation with 420 nm. Due to enhanced fluorescence activity, quantification becomes possible, even below a 1-ppm concentration of specific primary amine. A chemical matrix, formulated with the mixture of different concentrations of primary, secondary and tertiary amines, helps to differentiate and quantify primary amines present in the mixture, even at lower concentrations. This method is validated under synthetic field brine conditions to detect and quantify primary amines towards field applications.
Rafferty, Andrew (Scaled Solutions Ltd) | Stewart-Liddon, Christine (Scaled Solutions Ltd) | Simpson, Caroline (Scaled Solutions Ltd) | Hammonds, Paul (Scaled Solutions Ltd) | Graham, Gordon M. (Scaled Solutions Ltd) | Maskell, Phillip (Scaled Solutions Ltd)
It is known that some H2S scavengers have the potential to cause fouling either from reaction products or by the influence of their chemistry on brine scaling potential. A series of methods for assessing the performance of the H2S scavengers and the likely hood of the generation of unwanted reaction by products is described along with the utility of each test methodology under different production conditions
The performance of triazine- and aldehyde-based H2S scavengers are compared in a suite of laboratory tests, including liquid phase tests examining residual sulphides in solution and by measuring H2S in the gas phase using an
This work presents both apparatus and methods which can be used for the evaluation and comparison of H2S scavengers. It describes primarily experimental design aspects and challenges associated with differentiating between free (unscavenged) H2S and reacted (i.e. scavenged / trapped) H2S in bulk liquid phase tests often utilised for preliminary screening of scavengers and recommends a procedure to allow such tests to be conducted routinely. Works then compare results with more conventional gas stream monitoring approaches. This work presented and the approaches described will then assist in the screening and product selection process and provides information on the conditions under which un-desirable solid by-products may be generated.
Wang, Yefei (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Yang, Zhen (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Wang, Renzhuo (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Chen, Wuhua (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Ding, Mingchen (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Zhan, Fengtao (College of Science, China University of Petroleum East China) | Hou, Baofeng (School of Petroleum Engineering, Yangtze University)
A novel indolizine derivative inhibitor for acidization was introduced. It could exhibit effective corrosion inhibition at a much lower concentration without propargyl alcohol and shows economic and environmental advantages. From quinoline, benzyl chloride, and chloroacetic acid, two indolizine derivatives were prepared under certain conditions. These inhibitive indolizine derivatives were both synthesised from benzyl quinoline chloride (BQC), which one of the conventional quaternary ammonium corrosion inhibitors used for acidising. The target compound was purified and instrumental analysis methods including elemental analysis, high-resolution mass spectrometry (HRMS), and NMR were used to characterise the chemical structure. The inhibition performance of the indolizine derivatives in 15 wt.% HCl, 20 wt.% HCl, and mud acid (12%HCl + 3%HF) for N80 steel was investigated by weight loss measurement, electrochemical method (potentiodynamic polarization and EIS), and SEM surface morphology assessment.
When 0.1 wt.% indolizine derivative was added, the inhibition efficiency of N80 steel in 15 wt.% HCl at 90 °C increased to 98.8 % and 99.1 % respectively without the synergistic effect of propargyl alcohol: however, in terms of BQC, even at a dosage of 1.0 wt.%, the inhibition efficiency of N80 steel only reached 83.3 % under the same conditions. The novel derivative could impart an improved corrosion resistance effect. Compared with BQC, there are more active adsorption sites in the derivative and therefore the inhibitor could be better fastened to the steel surface. The firmly adsorbed inhibitors would thereby prevent the metal surface from making contact with H+ ions and finally increase the inhibitory effect. As a high-efficiency corrosion inhibitor, the novel indolizine derivatives may offer a new strategy for corrosion protection in acidising.
Hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine (MEA-triazine) is by far the most ubiquitous H2S scavenger used globally and occupies at least 80% of the available oilfield market. While almost the perfect scavenger in terms of kinetics and H2S uptake, this product does suffer from a number of undesirable effects which are usually tolerated or managed by various engineering modifications. For example, pH elevation causes scaling issues, deposition of intractable polymeric solids and increased ethanolamine load in crudes entering a refinery are some of the most prominent.
A new scavenging technology has been developed that offers an alternative to triazine. The guiding principles in the design of this technology were to achieve, equal or better scavenger efficiency compared to triazine, equal or better reaction kinetics compared to triazine, "best in class" solids control, minimal pH impact, cost competitive with triazine, no impact on fluid separation and minimal refinery impact. A family of products have been developed which are multicomponent systems, each having a designated function. The active scavenger is based upon a "latent" or hidden form of a small molecule scavenger (SMS), similar to a protecting group strategy in organic synthesis. The steady state active SMS concentration remains very low in the initial product, but it is released upon demand when it encounters hydrogen sulfide in its operational environment. The SMS release can be greatly enhanced using a suitable catalyst or synergist, over the base scavenger/carrier system, which enables a more efficient use of the base molecule. The quality and exact nature of the spent fluid is critically important to H2S scavengers and much effort has gone into the control and handling of the byproduct. High sulfur scavenger byproducts are almost always solid in nature and can cause numerous operational issues. MEA triazine has such a problem and polymerization of the initially formed monomeric dithiazine to amorphous dithiazine is one of the drivers to develop an alternative as is presented here.
This new suite of products has undergone successful field trials in both gas contact towers and direct injection applications. Some challenges have also arisen, as expected with any innovation, in other application areas and environments where unexpected issues have been encountered. An honest and informative account of the design, development, properties, field trial results and future direction for this exciting new technology are discussed as well as a critical evaluation against the aforementioned triazine industry benchmark.