bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Robust Analytical Development for Sulphonated Polymers in Oilfield Brines
Authors: MacKinnon Kirsty , Ewing Sarah J. , Graham Gordon M. 
Published: April 2016

Abstract
Residual scale inhibitor analysis in produced waters, particularly for the sulphonated co-polymers is recognised as an ongoing challenge for many operators and chemical suppliers. Early benchtop methods have been well used and documented (e.g. dialysis / Hyamine based techniques etc.) however are considered time-consuming and laborious. This is one of the key problems faced when assaying residual sulphonated polymers to ppm and sub ppm levels as separation of the inhibitor from the brine is often a difficult operation. This has led to the development of improved solid phase extraction techniques using anion exchange cartridges for sulphonated species in our labs as detailed in our previous works in SPE 131100. [1] In addition, chromatographic techniques including Gel Permeation Chromatography (GPC) [2] and various other methodologies (described in the literature as 2nd and 3rd generation approaches [3, 4]) have been developed. These have all focused on improving accuracy, speciation (assay of specific polymers in solutions containing residual levels of different polymers) and automation, thereby reducing the labour intensive nature and reducing the potential for human error.
This paper describes significant progression for the analysis of sulphonated co-polymers. The new methodology, based on ion pair (IP) chromatography, is more robust and utilises conventional C18 reverse phase columns which were previously disregarded as being completely ineffective for separation of the anionic sulphonated co-polymers. This marks a step change in our ability to isolate and detect sulphonated polymers utilising standard robust (and long wearing) C18 columns together with an ion-pair reagent.
This breakthrough followed an extensive search for alternative columns (including a variety of anion exchange columns) all of which proved fruitless for separation and repeatable, reliable assay of sulphonated polymers. This paper describes the development and effectiveness of this new technique and summarises the various alternative columns and HPLC approaches trialed prior to our successful development. Results from validation exercises and further developments have also been described.
Prediction of Sulphide Scales - Improvement of Our Understanding of Heavy Metal Sulphide Solubility
Authors: Saidoun M. , Mateen K. , Baraka-Lokmane S. , Hurtevent C. 
Published: April 2016

Abstract
An accurate scale prediction is crucial for the design of field production systems and treatment strategy. Existing models do not predict accurately ZnS and PbS scaling risks.
In this paper, we share the findings of using ScaleSoftPitzer (SSP2014) model, developed by Rice University, for this purpose. SSP has been extensively evaluated against both the relevant density and solubility data related to the carbonates, sulfates, and halide scales. However, it has not been closely evaluated against the sulphidic scales, due to lack of high quality experimental observations.
The evaluation of solubility as a function of multiple parameters is presented. Simulations results are compared to literature and field data. The method used to generate comparison is based on the total metal concentration at equilibrium. Temperature, pH, and composition are found to be strongly interplaying effects since aqueous phase metal complexes control the solubility of sulphide minerals. Chloride complexes are believed to be mainly responsible for metals aqueous speciation transport in oil and gas systems, however, hydrosulfide/sulfide complexes may play a role when pH increases or when brine salinity is low. The equilibrium measurements and extrapolated calculations are in reasonable agreement with field observations assuming sulphide minerals are in equilibrium with the produced brine at reservoir conditions. Research showed that colloidal dispersion phenomena and other specific interactions might play a significant role in metal sulphide systems; calcium seems to impact speciation. Two approaches are proposed to improve the model: (i) a short term solution using existing literature data to implement the principal complexes (ii) a more rigorous approach involving additional laboratory study acquisition of metal complexes.
A Systematic Investigation of Factors Affecting the Formation of Zinc Sulfide ZnS
Authors: Graham A. J. , Singleton M. A. , Sorbie K. S. , Collins Ian R 
Published: April 2016

Abstract
Work was undertaken to systematically investigate the factors that affect the formation of zinc sulfide in an aqueous system. Experiments were performed at a series of temperatures from room temperature up to 90 °C, at a range of initial pH values and in two brines systems. The effect of pH was further examined by changing the salt from Na2S.9H2O to NaSH.xH2O, therefore changing the initial sulfide source from S2- to HS-, as part of an ongoing method development strategy.
A variation of the standard barium sulfate static bottle test was used, in which the two bottles to be mixed contained aqueous "H2S" and zinc, respectively. Having pH adjusted the zinc brine to values calculated by the FAST sulfide model, the brines were pre-heated to the required temperature and mixed. Aliquots were removed at 2, 4 and 24 hours to perform elemental analysis by ICP and pH measurements were performed on all samples once they had returned to room temperature. In addition, particle size analysis and ESEM examination of the resulting precipitate were also performed for a subset of the samples prepared.
The reaction between zinc and aqueous "H2S" was quantitative at all temperatures up to 90 °C and in both brines. The final pH values of the supernatant were independent of the zinc brine pH and instead were dependent on the molar ratio of zinc and sulfide ions. A high pH, sulfide dominated, and a low pH, zinc dominated, plateau region were seen with a sharp inflection between the two. As a consequence, reaching field representative pH values was seen to be extremely difficult while retaining the ability to alter the relative concentrations of the reacting ions. Altering the sulfide source yielded the same trend, albeit with different absolute values. These observations have been rationalised with reference to the thermodynamic constants governing the reaction through scale prediction modelling.
The work presented here provides a greater understanding of the factors governing the formation of zinc sulfide scale and the considerations required for more industrially relevant formation and inhibition experiments in the future.
Analysis of Mineral Reactions Occurring in the Gyda Field Under Seawater Injection with the Help of Geochemical Non-Isothermal Model and Produced Water Data
Authors: Hu Yisheng , Mackay Eric 
Published: April 2016

Abstract
The evidence from the produced brine chemistry suggests that the Gyda field has experienced a variety of geochemical reactions due to the high temperature and initial calcium concentration, and so it is worth reviewing the produced water dataset and studying what in situ geochemical reactions may be taking place.
Produced brine chemistry data from 16 wells in the Gyda field are plotted and analysed in combination with general geological information and the reservoir description. A one dimensional reactive transport model is developed to identify the possible geochemical reactions occurring within the reservoir triggered by seawater injection, then extended with the inclusion of thermal modelling and also to be a two dimensional vertical cross section model.
Three possible classes of formation water compositions in different regions of the Gyda field have been identified by analysis of the produced water dataset. Anhydrite and barite precipitation are the two dominant mineral reactions taking place deep within the reservoir. Magnesium stripping may be a result of multi-component ion exchange, dolomite precipitation or a combination of both. Reservoir temperature is lowered during cold water injection. The solubility of anhydrite increases at lower temperature, and anhydrite will gradually dissolve in response to the movement of the temperature front, which is much slower than the formation/injection water mixing front. The extent of mineral precipitation within the reservoir can be reduced by the heterogeneity; the modelling shows that the extent of ion stripping caused by mineral reactions in the reservoir is greatest when simulating a single uniform layer. Brine mixing and the occurrence of geochemical reactions due to vertical mixing are not observable, even when assigning a high vertical permeability in a heterogeneous model.
Thermal modelling is included to evaluate the effect of non-isothermal processes and heat transport on the geochemical reactions, especially the anhydrite mineral reaction. We have investigated how the difference in horizontal permeability in the two layers affects brine mixing of formation and injection water and geochemical reactions.
Iron Carbonate Scaling on Hot Surfaces in Monoethylene Glycol MEG Solutions
Authors: Seiersten Marion , Beck Ralf 
Published: April 2016

Abstract
Monoethylene glycol (MEG) used as hydrate inhibitor in pipelines picks up corrosion products from carbon steel walls. This comes in addition to salts from produced fluids. Iron carbonate (siderite) scale can form on heat exchanger tubes when the MEG is heated and becomes supersaturated with respect to the solubility product of iron and carbonate. In this work a tube heat exchanger loop has been used to measure the scale growth rate of FeCO3 on hot surfaces simulating conditions typical for such heat exchangers. The scale growth rate was measured as function of skin temperature and FeCO3 supersaturation.
The temperature distribution in a tube heat exchanger is complex. The skin temperature is a function of the flow rate, temperature and heat capacities of the heating medium and the process fluids. In this work a tube heat exchanger model was used to calculate the skin temperature based on these parameters. The heat transfer to the test liquid depended on the MEG concentration in the liquid. The skin temperature in pure water was significantly lower than in MEG solutions at the same flow rate. This is mainly attributed to different viscosity. In the experiments, the flow rate on the MEG solution side was adjusted to achieve approximately the same Reynolds number for the various fluids to obtain comparable skin temperatures and flow patterns when the MEG concentration varied.
The FeCO3 supersaturation was adjusted to yield scaling only in the heated test section and avoid bulk nucleation and growth as well as scaling on other parts of the loop. MEG clearly decreases the scaling rate and the scale growth rate (Gscale) as a function of the supersaturation followed the equation: Gscale=kg⋅(Sskin−1)1.5 where kg is a MEG-dependent scale growth rate constant and Sskin is the supersaturation at the scale surface. The supersaturation is a function of the skin temperature, but the intrinsic effect of the skin temperature on the scaling rate was so small that it could be justified to ignore it in the expression.
The paper presents new knowledge on scale growth on hot surfaces in general and growth of iron carbonate in particular.
The Impact of Petrophysical and Completion Parameters on Production in the Denver-Julesburg Basin
Authors: Miller Fred , Payne Jon , Melcher Howard , Reagan Jim , Weijers Leen 
Published: April 2016

Abstract
The Denver-Julesburg (DJ) Basin has seen oil and gas production for more than a century. It is going through a new cycle of development with horizontal drilling and high-intensity hydraulic fracturing. Since the first horizontal wells in 2008 nearly 4,000 Niobrara and Codell horizontals have been drilled. While completion practices have remained fairly standard across the basin, production results vary wildly.
We utilized a high-quality digital log dataset to accurately characterize reservoir quality in the Niobrara and Codell formations in the DJ Basin. The final dataset included 562 digital logs spread across the current extent of horizontal drilling in the DJ Basin. A petrophysical workflow was developed and detailed mapping of the reservoir attributes was completed. The log derived parameters, along with an aeromagnetic and vitrinite reflectance dataset, provided excellent insight into which geologic parameters could be best tied to well production response.
Through bivariate and multivariate analyses using reservoir and completion data, and an economic evaluation to determine the "best bang for your buck", we have identified several completion changes for the basin that result in a significant reduction in the cost per bbl of oil produced. While geological parameters have been found to matter greatly for the production success of DJ horizontals, completions matter as well.
The high GOR areas of Inner Core Wattenberg benefit most from jobs with more proppant, whereas areas with poorer reservoir quality generally benefit from higher stage intensity and jobs with larger fluid volumes. All suggested completion changes have a major impact on lowering $/boe over the long term and result in lowering incremental cost per incremental boe within a period of only 365 producing days in the current low oil price environment.
Marcellus Wells' Ultimate Production Accurately Predicted from Initial Production
Authors: Male Frank , Marder Michael P. , Browning John , Ikonnikova Svetlana , Patzek Tad 
Published: April 2016

Abstract
The advent of horizontal drilling technology and hydraulic fracture completions has fundamentally altered the geometry of flow in shale gas systems, requiring new decline curves to forecast production. In this work we perform automatic decline analysis on Marcellus gas shale wells, and predict ultimate recovery for each well. We use a minimal model that captures the basic physics and geometry of the extraction process.
This model allows us to scale all individual wells' gas productions to fit upon a single, universal curve. This scaling curve predicts the production rate will decline as 1 divided by the square root of time early in the life of the well, and eventually rate declines exponentially. We fit cumulative production to the results of this model to determine time to boundary-dominated flow and ultimate recovery. For wells that have not entered boundary dominated flow, we use a new technique to estimate ultimate recovery, relying on early production.
We find 404 wells that are experiencing boundary-dominated flow. One would expect the time to boundary dominated flow varies due to well completion and reservoir properties. Instead, we find ultimate recovery in wells that have experienced boundary dominated flow is largely predicted by initial production, and time to exponential decline varies surprisingly little. Utilizing this information, we forecast gas production for 5,275 horizontal wells in Pennsylvania and West Virginia for a period of 25 years. We find that the median 25-year EUR is 3.6 Bcf with a standard deviation of 3.6 Bcf. The median time to interference is 3.9 years. From these results, we propose a new method for estimating time to boundary dominated flow for young wells. Our key discovery is that wells can have their EURs estimated early in life with surprising accuracy.
Slimhole Refracturing Case Studies and Experience Utilizing Mechanical Isolation for Effective Refracture Treatments
Authors: Hlidek B. , MacDonald D. , Gee C. , Makowecki B. 
Published: April 2016

Abstract
Refracturing or restimulation of existing producing wells is an economical option for increasing production when compared to new drills. However, stage isolation during restimulation of horizontal laterals can be a challenge, especially in wells with extended laterals and many perforated zones. This paper presents six case studies utilizing mechanical isolation technology for restimulation.
In some cases, existing wells may not have been effectively stimulated. Slimhole reentry systems have been successfully utilized to achieve mechanical isolation in horizontal laterals. This paper describes slimhole tool systems, the process of their installation, and the limitations. In order to evaluate refracturing success, initial post-fracture production of each well in the study is compared to post-refracture production data. The six case studies covered are from five different producing formations, covering locations in Alberta, British Columbia, Colorado and Texas.
This paper shows that slimhole refracturing technology is an effective method for restimulation. Stage isolation in existing producing wells can be reliably achieved using mechanical packer systems. In one of the Canadian examples, a producing well in the Montney formation in British Columbia was restimulated after more than three years on production. The resulting production increased from about 175 Mscf/D to a stabilized production rate of 700 Mscf/D more than 20 months after the restimulation. In San Juan County, Colorado monthly BOE increased 79 times after five months and in Limestone County, Texas monthly BOE increased 2.5 times after five months. In the Alberta Glauconite formation, production one year following restimulation resulted in over 435 MMscf of additional gas recovered.
Mechanical isolation packers are a viable and effective alternative to temporary isolation techniques for extended horizontal wellbores. Multiple formations, both oil and gas in United States and Canada are used as examples. Long term production is now available to validate refracturing benefits using slimhole systems that provide mechanical isolation.
Numerical Study of Proppant Transport in Complex Fracture Geometry
Authors: Han Jiahang , Yuan Peng , Huang Xu , Zhang Hao , Sookprasong Andy , Li Chunlou , Dai Yi 
Published: April 2016

Abstract
The key in unlocking unconventional reserves is to create massive fracture surface area. During the fracturing treatment, a huge volume of fracturing fluid is pumped to generate fractures and then followed with a large amount of proppant to provide enough conductivity for reservoir fluid to flow to the wellbore. The ultimate proppant distribution in the fracture system directly impacts well productivity and production decline rate. However, it is very challenging to predict how far proppants can go and where they will settle because of the complexity of the fracture system. Therefore, accurate modeling of proppant transport inside the fracture system is critical to enable stimulation optimization. Previous modeling and experimental studies were usually based on simple proppant settling velocity models and limited only to planar fracture cases. To accurately evaluate propped complex fracture systems, which are more common in unconventional reservoirs, advanced proppant transport models are required.
In this paper, proppant transport in various fracture geometries is investigated using computational fluid dynamics (CFD) models, in which the interaction between proppant particles and the carrying fluid phase is fully coupled to track proppant movement in the fractures. The planar fracture case is first investigated using a CFD model and benchmarked with results from commercial software. The CFD models are then used to simulate the proppant transport in T-junction and crossing-junction scenarios, which are often seen in unconventional reservoir fracture systems. Parametrical studies are also conducted to better understand how proppant transport is affected by fracture fluid viscosity, proppant density, and fluid injection rates.
The results from the proposed CFD models indicate that proppant transport within complex fracture geometries is significantly affected by fracture fluid dynamics and proppant properties. At fracture junctions, turbulent flow regime will develop, which helps proppant propagate to natural fractures. According to the parametrical studies, higher injection rate and light-weight proppant are beneficial in transporting proppant through fracture junctions to reach further in both hydraulic fractures and natural fractures.
Proppant transport models developed in this work fully incorporate the interaction between proppant particles and carrying fluid dynamics. This study extends the current understanding of proppant movement in complex fracture geometries and helps optimize hydraulic fracturing design to improve unconventional well production performance.
Mineralogy Derived Brittleness from the Qemscan: Niobrara Case Study
Authors: Katz David , Jung Marshall , Canter Lyn , Sonnenfeld Mark , Odegard Mark , Daniels John , Byrnes Alan , Guisinger Mary , Jones Kim , Forster John 
Published: April 2016

Abstract
The brittleness of sedimentary rocks is a critical aspect of their potential to form hydraulically stimulated fractures, resist embedment after stimulation, and thereby produce hydrocarbons over economically significant periods more efficiently. As such it is important to understand how brittle versus non-brittle rocks are organized within a play to improve the recovery of petroleum reserves by identifying higher potential stimulation intervals. The goal of this study is to document the link between the sequence stratigraphic hierarchy and its control on the evolution of mineralogy by FEI's QEMSCAN system, unconfined compressive rock strength, and dipole sonic derived brittleness for the Niobrara Formation. The Niobrara ultimately consists of a combination of sharply to diffusely bedded rocks composed of chalks to claystones with variable organic matter. It is mainly calcium carbonate rich with changing concentrations of detrital quartz, clay, and organic matter that function as the main variables of the mineral brittleness index. The detrital and organic components are relatively dominant in the transgressive systems tract (TST) in the form of laminated and sharply laminated-gradational millimeter to centimeter to decimeter intervals of organic rich chalky claystones-to-marly chalks; high resolution scanning electron photomicrographs also document that this fine scale bedding continues at the nanometer to micrometer scale. Discretely interbedded chalks and marly chalks are interbedded with marls at the cm to decimeter scale during the highstand systems tract (HST); by HST time the shorelines have been pushed landward the furthest and detrital terrestrial contribution to the marine environment has been reduced. This environment is ultimately more favorable to chalk deposition and an overall more brittle mineral assemblage. Mineral derived brittleness logs of the Niobrara ultimately covary with dipole sonic derived rock mechanics (Young's Modulus and Poisson's Ratio), unconfined compressive rock strength measurements from the Equotip-Piccolo, and gamma ray values from downhole tools which in turn may be tuned to identify hydraulic stimulation targets away from cored wells.