Case Study: Single-Aqueous-Phase Retarded Acid Performance Offshore Sarawak

The purpose of acid stimulation of carbonate formations is to increase production. The essential component for these stimulation fluids is the carbonate-dissolving agent, which creates conductivity channels connecting the reservoir with the wellbore. Controlling the reactivity of hydrochloric acid (HCl), the most-used dissolving agent due to its high dissolving capacity, wide availability, and low unit cost, is the most viable approach to successfully stimulate a high-temperature carbonate reservoir. It is essential to retard the HCl-carbonate rock reaction to achieve the optimum balance between total fluid used and enhanced well production. It is well documented that the conventional emulsified acid exhibits high friction pressure, is cumbersome to prepare, and performs with sensitivity to a multitude of parameters. These drawbacks have prevented the industrywide adoption of this method. The recently developed single-aqueous-phase retarded acid (SAPRA) designed for primarily 15–25% HCl solutions represents a significant step forward. The first successful field implementation of SAPRA took place offshore the Malaysian state of Sarawak in early 2021. At Sarawak, the HCl reactivity was regulated and retarded by a single potent low- dosage additive, which is compatible with selected acid corrosion inhibitors, nonemulsifiers, H2S scavengers, other commonly used additives, and if necessary, friction reducers. Improving Acid Stimulation Efficiency The technical approach behind SAPRA is based on chemical technology that enables the reduction of the reaction rate and allows the control of the diffusion/mass transfer mechanism. This is key in designing the acid treatment to optimize chemical program cost and well production and has been extensively studied (Al Moajil et al. 2020; Czupski et al. 2020; Daeffler et al. 2018; and Abdrazakov et al. 2018). The technology was developed utilizing a surface barrier concept where transiently adsorbed retarder molecules adhere to a carbonate surface and thus, delay the hydrogen ion carbonate reaction over a range of acid concentrations and operating temperatures. Due to the complexity of the chemical interactions among all the additives in the acid fluid system, the selected additives must be screened to ensure mutual compatibility before conducting performance testing such as corrosion rate, calcite solubility capacity characterization, and coreflow measurements. Incompatible chemistry could lead to severe corrosion issues such as the examples shown in Table 1.

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New and Improved Single-Aqueous-Phase Retarded Acid SAPRA - Performance, Pore Volume Break through, and Wormhole Characterization

10.2118/206363-ms ◽

2021 ◽

Author(s):

Jing Wu ◽

Matthew Monette ◽

Jeff Sickorez ◽

Joseph Street ◽

Peng Tonmukayakul ◽

...

Keyword(s):

Corrosion Inhibitors ◽

Acid Corrosion ◽

Carbonate Reservoir ◽

Laboratory Findings ◽

Well Production ◽

And Performance ◽

Viable Approach ◽

The Right ◽

Optimum Balance ◽

Low Dosage

Abstract Controlling the reactivity of HCl is the most viable approach to successfully stimulate a high-temperature carbonate reservoir. It is essential to retard the HCl-carbonate rock reaction to achieve the optimum balance between total fluid used and enhancing well production. However, drawbacks intrinsic to the technology architectures have prevented the industry-wide adoption of these inventions. For instance, the conventional emulsified acid is well documented to exhibit high friction pressure, is cumbersome to prepare, and performance is sensitive to a multitude of parameters. The recently developed singleaqueous-phase retarded acid (SAPRA) represents one big step toward the right direction, but there is certainly ample room for improvement. This paper presents the next generation of SAPRA system and its laboratory findings. In this system, the HCl reactivity is regulated and retarded by a single, potent low-dosage additive, which is compatible with selected acid corrosion inhibitors, non-emulsifiers, H2S scavengers, and other commonly used additives, and if necessary, friction reducers as well.

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Dynamic Variation of Water Saturation and Its Effect on Aqueous Phase Trapping Damage During Tight Sandstone Gas Well Production

ACS Omega ◽

10.1021/acsomega.0c04993 ◽

2021 ◽

Vol 6 (8) ◽

pp. 5166-5175

Author(s):

Juan Miao ◽

Chuanrong Zhong

Keyword(s):

Aqueous Phase ◽

Water Saturation ◽

Tight Sandstone ◽

Gas Well ◽

Dynamic Variation ◽

Well Production

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Control of Inhibitor Squeeze Through Mechanistic Understanding of Inhibitor Chemistry

SPE Journal ◽

10.2118/87450-pa ◽

2006 ◽

Vol 11 (03) ◽

pp. 283-293 ◽

Cited By ~ 23

Author(s):

Mason B. Tomson ◽

Amy T. Kan ◽

Gongmin Fu

Keyword(s):

Carbonate Reservoir ◽

Scale Inhibitor ◽

Control Scale ◽

Rock Interaction ◽

Well Production ◽

Low Concentrations ◽

Production Wells ◽

Brine Chemistry ◽

Reservoir Type ◽

Solid Phases

Summary Chemical scale inhibitors are commonly used to prevent or inhibit scale formation in production. The most economic treatment of scale inhibitor is normally through chemical squeeze. However, there is little agreement regarding the primary mechanism by which the threshold scale inhibitors are retained in producing oil or gas formations as a result of squeeze procedures. Recent advances in phosphonate/rock interaction research at the Rice U. Brine Chemistry Consortium have significantly improved our knowledge of what controls inhibitor placement in the formation. It is commonly suggested that reservoir type determines how an inhibitor is retained in a formation. Our research suggests that the pill chemistry is also an important determinant for retention of carbonate reservoir. Acidic pills are mostly retained near the wellbore, while more neutralized pills move farther into the formation. Three calcium nitrilomethylenephosphonate (NTMP) solid phases, an amorphous phase, and two crystalline Ca2.5HNTMP phases with pKsp = 22.6 and pKsp = 24.2, are particularly important for inhibitor retention. The relative sizes of these solid phases formed are governed by the pill composition and acidity. These results can be explained by a solution-phase-controlled sequence of reactions. All of this information has been incorporated into a new squeeze-design software program, Squeeze SoftPitzer. Introduction Threshold scale inhibitors, such as the phosphonates, polyacrylates, and polymaleates have been used to control scale since 1936 (Rosenstein). Preferable to sequestering agents, which must be added in stoichiometric amounts to inhibit precipitation, chemical threshold scale inhibitors generally require the addition of only a few milligrams per liter to inhibit scale. Inhibitors are commonly applied to production wells through an inhibitor squeeze. An inhibitor squeeze is performed by pushing scale inhibitor solution into a producing formation and fixing the inhibitor in the formation. When well production begins, inhibitor is produced along with the formation water. Following the squeeze, scale inhibitor flows back at low concentrations, which increase and peak rapidly to some value and then decline within a few days to a low plateau concentration, which comprises the bulk of the squeeze duration. The plateau flowback inhibitor concentration is normally sufficient to inhibit scale.

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An Evaluation of the Performance of Chainsaw Lubricants

Croatian journal of forest engineering ◽

10.5552/crojfe.2020.689 ◽

2020 ◽

Vol 41 (2) ◽

pp. 325-332

Author(s):

Alex Orawiec ◽

Levi Suryan ◽

John Parmigiani

Keyword(s):

Tribological Properties ◽

Hydrodynamic Lubrication ◽

Unit Cost ◽

Cutting Speed ◽

Performance Testing ◽

Wear Test ◽

Flash Point ◽

Lubricating Oil ◽

Motor Oil ◽

Additional Information

Chainsaws require lubrication of the guide bar and saw chain to function properly. Many oils are commercially available to provide this lubrication. Economical and more recently environmental concerns are increasingly compelling consideration of the best type of oil to use. Several published scientific studies provide some guidance, but additional information is needed for operators to make informed and effective choices in lubricating oil selection. The work presented in this paper contributes to providing this guidance by comparing the performance of economy and premium versions of three commonly-used types of lubricating oils: petroleum-based bar-and-chain oil, biodegradable bar-and-chain oil, and petroleum-based motor oil. Testing was conducted on a laboratory chainsaw test apparatus used in prior published scientific studies of chainsaw performance. Testing consisted of free running (i.e. chain traveling about the bar at cutting speed but not cutting) for a prescribed time period, while lubricating oil was applied to the guide bar and saw chain in the usual manner and at typical flow rates. Based on the correlations between wear, friction, and temperature, the mean guide bar temperature was used as the measure of performance of each oil. Results showed that, while each oil type performed adequately, the petroleum-based bar-and-chain oil performed best and the biodegradable-based oil performed worst with the petroleum-based motor oil providing intermediate performance. No consistent correlation was found between either the unit cost of each oil and its performance or the perceived quality of each oil (economy versus premium) of each oil and its performance. Tribological properties of flash point, viscosity, and four-ball wear were measured. A weak correlation was found between flash point values and performance. A possible Stribeck relationship was found for viscosity implying a possible transition from mixed and hydrodynamic lubrication. No correlations were found between performance and four-ball wear test results. These results support chainsaw operator observations and other published scientific findings that a variety of oils can be effectively used as lubricants. The lack of correlation of performance with some commonly-measured tribological properties suggests lubricating-oil providers should consider the use of a dedicated saw chain testing apparatus in product development.

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Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078699 ◽

1977 ◽

Vol 35 ◽

pp. 232-233 ◽

Cited By ~ 1

Author(s):

P. Trebbia ◽

P. Ballongue ◽

C. Colliex

Keyword(s):

Electron Microscope ◽

Energy Loss ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Single Channel ◽

Detection System ◽

Surface Barrier ◽

Solid State Detector ◽

Electrostatic Mirror ◽

Electron Energy Loss

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

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