bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guar Replacement with Synthetic Polymers - Utica Shale Case Histories
Authors: Blamble E. A. , Pyncheon J. 
Published: January 2016

Abstract
This study was conducted to determine the advantages of replacing guar-based polymers with polyacrylamide (PAM) engineered polymers in unconventional shale gas plays. Hydraulic fracturing of unconventional shale gas reservoirs usually consists of low-viscosity slickwater treatments where the water/sand mixture is pumped into the reservoir at high treatment rates (80+ bpm). At such high fluid velocities, the proppant/water slurry is abrasive to fracturing equipment resulting in decreased service life plus higher repair and maintenance costs. Additionally the low-viscosity slurry will allow proppant to fall out of suspension. This causes poor proppant placement in the fracture, leading to decreased well production response. In these situations it is advantageous to use a hybrid design where guar polymers are added to the slurry to increase viscosity and aid in maintaining suspension of the sand. The disadvantage of using guar-based polymers for this application is a polymer residue is left in place following the fracturing treatment, which can decrease the production of the well.
A guar-alternative, PAM, has been developed for use as a friction reducer in slickwater treatments and to increase the viscosity of the water/sand mixture when added in increased concentrations. This PAM has been specifically engineered so that the polymer chain can be broken into discrete units using traditional oxidative breakers and then flowed back out of the well when production begins. This breaking mechanism leaves behind less polymer residue than old-style guar treatments. This system has been used numerous times in the Utica shale and has resulted in superior production performance versus the wells that have been completed in the same area using guar polymers.
This paper will focus on multiple Utica shale wells that have been successfully completed using the PAM engineered polymer scheme. Production data on a statistically significant number of offset wells will be presented, drawing from publically available production data. Production periods of up to 2 years will be included to illustrate the advantages this system has over the traditional hybrid fracturing using guar-based fluid systems. Data will be provided which demonstrates that wells completed using this PAM system produce, on average, 66% more hydrocarbons than offset wells completed using conventional systems.
This paper will demonstrate that there is an effective alternative to guar gel available for use in hydraulic fracturing operations. This alternative solution leaves behind significantly less polymer damage, enhances fracture conductivity, and improves hydrocarbon production.
An Improved Wormhole Propagation Model with a Field Example
Authors: Tan Xuehao , Weng Xiaowei , Cohen Charles-Edouard 
Published: January 2016

Abstract
An improved 1D-averaged model for wormhole propagation was developed that considers acid spending and leakoff along wormholes. The 1D-averaged type of model is one of several types that have been developed for predicting wormhole propagation during matrix acidizing treatment in carbonates; other models include discrete models, Darcy-scale 2D and 3D continuum models, and multi-pore-scale network models. Among these models, the 1D-averaged model is commonly applied in acidizing simulation software because of its simplicity.
Most of 1D-averaged models are based on the pore volume to breakthrough correlations developed from core flooding experiments on different rock samples and acid systems. It is also generally assumed that the effect of acid spending is already included in the experimental results. Although this is a reasonable assumption when the wormhole length is shorter than the core length (typically 6 in.), once wormhole penetration is longer than 6 in., the acid spending becomes more significant while acid travels along wormholes due to the reaction between acid and the side walls of wormholes. Meanwhile, acid leak-off through wormhole walls becomes an important factor for longer wormholes. Not considering acid spending and leakoff in relatively longer wormholes may result in overestimation of wormhole penetration depth.
In our model, we adopted an empirical correlation to determine the leak-off velocity profile along wormholes. Then, we developed a numerical model to simulate the non-uniform acid concentration along wormholes. Both the empirical correlation for leak-off velocity profile and the numerical model for acid concentration are validated by comparing to published materials and an independent computational fluid dynamics (CFD) software. As expected, wormhole penetration predicted by the new model shows shorter wormholes than the traditional 1D-averaged model.
We applied the new model to a field case and showed its capability of reasonably matching the downhole pressure during acidizing treatments and PLT data before and after acidizing treatments, which demonstrates the applicability of the model to job design and interpretation in the field.
Analysis of Sand Screen Integrity in Depleting Sandstone Reservoir
Authors: Tallin Andrew , Han Yanhui , Wong George 
Published: January 2016

Abstract
In this paper, sand screen integrity in two depleting reservoirs is evaluated using fluid-mechanical coupling analysis. Both analyses use a numerical model for rock-structure interaction. In the first, a horizontal completion in a soft sandstone reservoir is evaluated. This analysis used laboratory tests to measure the properties of ceramic proppant, the formation sandstone and sand screen. The numerical model included friction hardening and volumetric hardening of the formation, friction hardening of the gravel pack, and the crushing strength of the screen base pipe which were all measured in the laboratory. In the second, a vertical gravel pack in a stiff strong formation was analyzed to evaluate gravel screen contact loads under very high levels of depletion and drawdown. While this analysis did not include a laboratory program, using instead existing core data, it did model the effect of near wellbore damage on the contact load.
The results show that loads on sand control completions can be estimated and the workflow demonstrated here is a way to select durable sand control completions.
Solubility of Barium Sulfate in Formate Brines - New Insight into Solubility Levels and Reaction Mechanisms
Authors: Howard Siv , Anderson Zhao , Parker Stuart 
Published: January 2016

Abstract
It has been known since the 1930's that concentrated brines release barium into solution from barite. The amount of barium released into solution is a function of the molar salt concentration, brine type, temperature, and pressure. Brines containing very high molar concentrations of solute are the most effective at solubilizing barite in well operations. Given the HSE hazard posed by fluids containing soluble barium it is important to know exactly what levels of this heavy metal may be present in high molarity oilfield brine systems that have been contaminated with barite.
An extensive test program has now been conducted to provide new and reliable information on the soluble barium content of potassium- and cesium formate brines that have been exposed to analytical grade barium sulfate at elevated temperatures and then cooled. The effects of formate concentration and the ratio of cesium to potassium in the formate brines were investigated. The brines were tested with and without the addition of carbonate/bicarbonate pH buffer, as a function of exposure temperature and exposure time.
The results of this research confirm results of previous research reported by Shell, indicating that up to 3,500 mg/L of barium can be released from barium sulfate at 100°C (212°F) in the most concentrated potassium formate brines. However, the good news is that soluble barium levels are low in all formate brines that contain carbonate/bicarbonate pH buffer. This is because any dissolved barium will precipitate out as barium carbonate, which is barely soluble in concentrated formate brines.
This new insight into the mechanisms of barite dissolution in buffered and unbuffered formate brines could open the door for the formulation of more advanced fluids for filter cake removal and scale dissolution applications.
Gravel Pack Sizing Criteria - It's Time to Re-Evaluate
Authors: Fischer Christine , Constien Vernon , Vining Carla 
Published: January 2016

Abstract
Correct sizing of Gravel packs for sand retention in Gravel Pack and Frac Pack completions has been a controversial topic for many years dating back to the 1960's. One of the earliest studies completed, and still most often cited, was by Saucier in 1974. Saucier proposed sizing the gravel based on the median size of the formation (d50 * 6). The Saucier criteria is still often used and works well for many applications. In 1998, Tiffin furthered the Saucier work in SPE 39437 and suggested that for some specific formation sands, the gravel could be size as much as 7–8 times the median size of the formation. In both bodies of work, the median size of the formation is really the only formation size parameter that is considered in the gravel pack size selection.
In the ensuing years, much has been published regarding sand retention testing, but the criteria for gravel pack size selection has not been updated or addressed. In 2012 Martch et al. suggested a new method which correlated sand retention data to a ratio of the effective formation size and the gravel pack pore size (SPE 151865).
In this series of work, the gravel pack pore size is further evaluated using the permeability of the gravel pack and other methods. A new sizing method is proposed which is based on the "effective formation size", (Formation d50 / Uniformity Coefficient) as well as the gravel pack pore size. In this manner, the gravel pack is effectively treated like a screen and the selection of gravel pack size becomes similar to the selection of screen size.
The sand retention testing used to validate this selection criteria was performed using both constant drawdown and constant rate test methods. These represent the two most common methods used in the industry. The amount of solids produced, the size of the solids produced, and the initial and final gravel pack permeability are measured and reported for each test.
Would You Like Good Lab Results or a Productive Well? Getting Wellbore Cleanup Testing Right!
Authors: Fischer C. C. , Vining C. , Constien V. 
Published: January 2016

Abstract
Soft sand wells are typically more expensive completions due to the need for sand control. The sheer cost of the wells makes the completions more high risk and increases the need for laboratory testing to validate the screen or gravel pack sizing as well as drill-in fluid selection and filtercake cleanup.
Laboratory simulations of actual wellbore conditions to determine the effectiveness of wellbore cleanup treatments is quite complex. When the formation is unconsolidated and requires sand control such as screen only or gravel pack, the complexity increases further. Typical core flood equipment does not adequately confine the formation material to allow drilling and cleanup fluids to be circulated at representative shear rates and pressures over the formation face.
The paper summarizes over 15 years of work to develop procedures for dynamic drill-in fluid flow testing in a screen-only or gravel pack scenario. The suite of tests has been successfully used for multiple operators in order to determine the effects of drill-in fluids with unconsolidated and consolidated formation as well as to optimize clean-up treatment and gravel pack performance. This results in selection of least damaging drill-in fluids and better filtercake removal.
Dynamic flow cells have been designed to enable laboratory testing to be performed under matching wellbore conditions. This dynamic flow test method is unique because it has true slot flow that enables the filtercake to be deposited on the face of an unconsolidated formation pack. The well conditions are received from the client and the shear rate at the formation face is calculated and matched in the laboratory. Another unique aspect of the design is the ability to form the drill-in fluid filtercake on multiple test cells simultaneously.
Once the drill-in fluid filtercake is established, it is equally important to be able to simulate filtercake clean up treatments under laboratory conditions. The test method allows for multiple flushes across the filtercake to simulate the entire clean-up system. The flushes may include solids-free mud, push pill, clean oil or brine, and a reactive clean-up treatment, depending upon the drill-in fluid being tested. Multiple cleanup treatments can be applied to the filtercake, again matching the shear rate and temperature as indicated by the client well conditions. When a gravel pack is present, the cell design allows the gravel pack to be placed after the filtercake is built on the formation sand. Then, the clean-up treatment is circulated to the back side of the screen. The test method also allows for extended treatment soak times, up to 10 days.
Evaluating Damage to the Proppant Pack from Fracturing Fluids Prepared with Saline Water
Authors: Prabhu Rasika , Hutchins Richard , Makarychev-Mikhailov Sergey 
Published: January 2016

Abstract
Polymer gels used in hydraulic fracturing to generate fracture geometry and ensure proppant transport are also known to damage the proppant pack permeability, and this damage reduces the well production rate. As reuse of produced water and other highly saline water sources for fracturing applications grows, there is further damage expected from scale/precipitate deposition into the proppant pack. Past studies in the literature focus on impairment of proppant pack permeability from broken polymer gel residue, but precipitation of scale from source water is not considered. The objectives of this study are (i) to develop laboratory methods of assessing conductivity reduction from different fluid-based factors such as polymer residue and scale and (ii) to develop correlations to predict retained permeability based on simplified measurements. The simple methods will minimize the need for the standard conductivity testing, which can be time consuming, expensive, prone to significant test-to-test variation, and still subject to experimental artifacts. By the use of simplified procedures, the cost of conductivity testing can be reduced while allowing validation of the simplified method results.
We demonstrate a simple benchtop method to measure permeability of a proppant pack damaged by polymer residue, scale, or both. This method provides an opportunity to study a specific damage source in isolation, where the test is not influenced by problems such as spatial inhomogeneity of gel break, ineffective cleanup of filter cake, creation of proppant crush fines, etc., that are inherent in conventional API-type conductivity tests.
Experimental measurements of retained permeability arising from different sources such as polymer residue and scale were compared with traditional conductivity measurements. They were also correlated with empirical permeability models that rely on proppant pack porosity.
One key insight from the new, simplified method for proppant damage assessment is that the loss of permeability correlates with porosity reduction from polymer residue volume with a similar extension to scale precipitation.
An Assessment of an Uncomplicated Drill-in Fluid and Its Application to a Wide Range of Global Completions and Their Recent Successes
Authors: Luyster M. R. , Tresco K. , Dobson J. , Ravitz R. , Allogo C. M. , Lim K. Sooi 
Published: January 2016

Abstract
An established non-biopolymer reservoir drill-in (NBRDF) system which was developed in very early 2000 for high-density drilling applications – approximately 11.5 to 17.5 lbm/gal – was recently improved to provide functionality in low-density drilling applications – as low as 9.5 lbm/gal. Global implementation of this system over the last several years has demonstrated not only flexibility with respect to drilling and completing in diverse reservoirs but also its application as a workover system. In addition, this system was recently optimized by incorporating compatible chemistry to mitigate atypical damage mechanisms. As such, several case histories are presented to demonstrate the system's broad functionality with respect to density, completion type, reservoir, and logistics, as well as its capacity to reduce near-wellbore/formation damage.
This non-biopolymer reservoir drill-in fluid (NBRDF) system demonstrates relatively high tolerance to solids and reservoir fluids as well as ease of hydration when mixing on the rig. Routinely the hydraulics are consistent and predictable even as no biopolymer is utilized. This system is compatible with the incorporation of an inhibitor, specifically, a scale inhibitor to mitigate calcium carbonate and minor sulfate scaling. This system recently incorporated a sized calcinated magnesium compound (MC2) and sized magnesium complex (MC3) which promotes viscosity, specifically low-shear rate viscosity, at a lower density range that was not achievable before.
The initial concepts of buoyancy of solids and the exclusion of a biopolymer as incorporated in relatively high-density brines formed the basis for the development of this system. These concepts are discussed first to provide a background for the preceding recent improvements and case histories.
Each case history presents a different set of objectives whereby pre-planning assessments were implemented to address and mitigate perceived risks as related to the fluids. The methods employed include assessments for rheology, scaling, hydraulics, displacements, compatibility and formation damage. The drilling and completion results for these projects exhibit a wide range of applications as well as flexibility with respect to required density, completion hardware and reservoir type. The procedures utilized for each project are evaluated with respect to specific drilling and completion targets and include the iterations/modifications required; subsequently the field learnings are also discussed.
Relating Quantitative Soil Structure Metrics to Saturated Hydraulic Conductivity
Authors: Eck Dennis V. , Qin Mingming , Hirmas Daniel R. , Giménez Daniel , Brunsell Nathaniel A. 
Published: January 2016

Core Ideas
Soil structure quantified in the field using a 3D laser scanning technique (MLT).
MLT data and coefficient of linear extensibility combined into a structure metric.
Soil water contents recorded at four depths in a field lysimeter and used in HYDRUS‐1D.
Saturated conductivity (Ks) estimated with a Markov chain Monte Carlo approach.
New metric better correlated to Ks in horizons with strong soil structure.
Soil structure affects saturated hydraulic conductivity (Ks) by creating highly conductive macropores that preferentially transmit soil water. In this study, we explored the relationship between Ks and macropores in an Oxyaquic Vertic Argiudoll in northeastern Kansas. Macropores were quantified from an excavation wall using multistripe laser triangulation (MLT) scanning. Soil water contents were measured at four depths within a soil lysimeter installed within 2 m of the MLT‐scanned soil profile and adjacent to an Ameriflux tower monitoring precipitation, air temperature, and solar radiation. Selected hydraulic properties of soil horizons within the lysimeter were optimized to water content data using a Markov chain Monte Carlo technique in combination with the mobile–immobile water (MIM) model in HYDRUS‐1D. Estimates of Ks varied between 4198 cm d−1 in the A horizon and 0.6 cm d−1 in a 2Btss2 horizon with strongly expressed wedge structure. Approximately 87% of the variation in Ks was explained by the geometric mean of the widths of pores quantified with the MLT technique and modified by the coefficient of linear extensibility (COLE). The use of the COLE allows the widths of the macropores obtained under dry conditions to be approximated at saturation. Two models that predict Ks from either texture or water retention data resulted in Ks estimates that were similar to each other but significantly lower than Ks values predicted with MIM in horizons where structural pores dominate water flow. This technique shows a great deal of promise in better understanding and predicting the relationship of soil structure to water flow.
Evaluation of a Direct‐Coupled Time‐Domain Reflectometry for Determination of Soil Water Content and Bulk Electrical Conductivity
Authors: Schwartz Robert C. , Evett Steven R. , Anderson Scott K. , Anderson David J. 
Published: January 2016

Core Ideas
TDR‐315 sensors could be calibrated using conventional TDR methodologies.
Soil water content calibrations using conventional TDR and TDR‐315 were comparable.
Measured travel time using TDR‐315 was insensitive to soil electrical conductivity.
Signal degradation in coaxial cables and interconnects is a long‐standing problem in the practical deployment of time‐domain reflectometry (TDR) for soil water monitoring. Acclima, Inc. has recently commercialized a TDR sensor (TDR‐315) with all electronics required for waveform acquisition embedded in the probe head. We calibrated ten TDR‐315 sensors and conventional TDR for apparent permittivity (Ka) and bulk electrical conductivity (σa) measurements. Also, soil water content calibrations were completed for a Pullman (fine, mixed, superactive, thermic torrertic Paleustolls) clay loam soil. Lastly, the sensitivity of Ka to σa was examined using a saturated solute displacement experiment with both probe technologies installed in a column packed with Pullman clay loam. A range of σa (0.65–2.8 dS m−1) was established by equilibrating the column with 0.25 dS m−1 CaCl2 and introducing a step pulse of 7.3 dS m−1 CaCl2. Permittivity calibrations of the TDR‐315 could be accomplished with conventional TDR methods and with similar sampling errors. Conventional calibrations of σa using long time amplitudes yielded a linear response for σa ≤ 3 dS m−1, above which the response was nonlinear. The fitted water content calibrations of the Pullman clay loam for the TDR‐315 were nearly indistinguishable from conventional TDR calibrations with similar root mean square errors (0.017–0.020 m3 m−3). Response of the two measurement technologies in a lossy soil during changing solution conductivities demonstrated that, in contrast to conventional TDR, travel time measured using acquired TDR‐315 waveforms was insensitive to σa up to 2.8 dS m−1.