Two strategies are applied to mimic the ampholytic nature of the surfaces of half-generation PAMAM dendrimers and yet retain the very narrow dispersity inherent of triazine dendrimers. Both strategies start with a monodisperse, single-chemical entity, generation two triazine dendrimer presenting twelve surface amines that is available at the kilogram scale. The first method relies on reaction with methyl bromoacetate. Complete conversion of the surface primary amines to tertiary amines occurs to provide 24 surface esters. Extended reaction times lead to quarternization of the amines while other unidentified species are also present. The resulting polyester can be quantitatively hydrolyzed using 4M aqueous HCl to yield a dendrimer with 12 tertiary amines and 24 carboxylic acids about a hydrophobic triazine core. The second method utilizes Michael additions of methyl acrylate to yield 24 surface esters. This reaction proceeds more rapidly and more cleanly than the former strategy. Hydrolysis of this material proceeds quantitatively using 4M aqueous HCl to yield desired dendrimer. In both cases, MALDI-TOF mass spectrometry provides compelling evidence of reaction progress. Electrophoretic analysis confirms the ampholytic nature of these materials with the former targets having a pI value in the 1.8 < pI < 3.4 range, and the latter having a pI value in the 4.7 < pI < 5.9. These ranges bookend the pH range within which PAMAM dendrimers become zwitterionic, 3.4 < pI < 4.7. The strategy of using monodisperse amine-terminated dendrimer constructs as core offers significant advantage over PAMAM homopolymers including dispersity, ease of characterization and batch-to-batch reproducibility. These triazine dendrimers could ultimately be adopted into materials with applications wherein the demands of purity have hitherto remained unsatisfied.

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Summary Hydraulic fractures can enhance well productivity from stress-sensitive naturally fractured reservoirs, such as coalbed methane or coal seam gas (CSG) reservoirs. Graded proppant injection (GPI) has been proposed to enhance long-term, far-field interconnectivity between the created hydraulic and short-term, enhanced natural fracture permeability, resulting from fracture fluid leakoff and lowered net effective stress. This novel study shows how applying GPI with hydraulic fracturing treatments resulting in an increased stimulated reservoir volume (SRV) can enhance well productivity and improve CSG well economics. A commercially available reservoir model and history-matched hydraulically fractured coal seam case are used to evaluate well performance differences between a hydraulic fractured reservoir and one including GPI application. A dual-porosity system and the Palmer and Mansoori model are used to simulate initial and long-term permeability accounting for reservoir depletion (i.e., increased net effective stress and matrix shrinkage). A previously validated case study is used to describe the post-embedment benefits of GPI based on the porosity model and history-matched reservoir properties. A net present value (NPV) can then be calculated for each scenario, based on the production differences and typical Australian CSG costs. Our results show that permeability enhancement is achieved beyond the hydraulically fractured region for all post-GPI stimulation cases. An optimal SRV can be found relative to permeability that maximizes the incremental NPV from GPI application. The next most significant parameters after permeability that influence the economic outcomes are fracture porosity and coal compressibility. A larger SRV yields higher cumulative gas production over 30 years with up to 7.2 times increase over gas production without GPI. This study substantially increases our understanding of how to model and understand the benefits of GPI application along with hydraulic fracturing to increase the SRV in CSG wells.

Summary In coal-seam-gas (CSG) fields, where single wells tap multiple seams, it is likely that some of the individual seams hardly contribute to gas recovery. This study aims to examine the contribution of individual seams to the total gas and water production considering that each seam can have different properties and dimensions. A sensitivity analysis using reservoir simulation investigates the effects of individual seam properties on production profiles. A radial model simulates the production of a single CSG well consisting of a stack of two seams with a range of properties for permeability, thickness, seam extent, initial reservoir pressure, coal compressibility and porosity. The stress dependency of permeability obeys the Palmer and Mansoori (1998) model. A time coefficient (α) relates seam radius, viscosity, porosity, fracture compressibility, and permeability. It is used to aid interpretation of the sensitivity study. Finally, two hypothetical simulation scenarios with five seams of different thicknesses and depths obtained from producing wells are explored. The range in properties represents conditions found in the Walloon Coal Measures (WCM) of the Surat Basin, relevant to the Australian CSG industry. Each seam in the stack achieves its peak production rate at different times, and this can be estimated using α. Seams with lower α reach the peak gas rate earlier than those with higher α-coefficient. The distinct behavior of gas-production profiles depends on the combination of individual seam properties and multiseam interaction. At a αratio &gt; 1 (i.e., αtop/αbottom &gt; 1), the bottom seam peaks first but achieves lower gas recovery than the top seam. An increasing αratio is associated with the inhibition of less-permeable seams and reduced overall well productivity. For αratio &lt; 1, the top seam experiences fast depletion and total gas-production rates decrease drastically. This outcome is confirmed by a more realistic scenario with a higher number of coal layers. Poor combination of seams leads to severe production inhibition of some coal reservoirs and possible wellbore crossflow. The contrast of the seam-lateral extent in the stack and fracture compressibility play an important role in well productivity in the commingled operation of a stack of coal seams. Unfortunately, the lateral extent of individual coal seams is difficult to estimate and poorly known and, therefore, represents a major uncertainty in gas-production prognosis. The αratio analysis is a useful tool to gain understanding of modeled well productivity from commingled CSG reservoirs.

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Defining pressure dependent permeability (PDP) behaviour in coalbed methane (CBM) or coal seam gas (CSG) reservoirs using reservoir simulation is non-unique based on the uncertainty in coal properties and input parameters. A diagnostic fracture injection test (DFIT) can be used to investigate bulk permeability at a reservoir level and at lowered net effective stress conditions. As coal has minimal matrix porosity and under DFIT conditions cleat porosity is fluid saturated with reasonably definable total compressibility values, the DFIT data can provide insight into PDP parameters. At pressures above the fissure opening pressure, pressure dependent leak off (PDL) behaviour increases exponentially with increasing pressure. Many authors have noted that with decreasing pressure PDP declines exponentially with increasing net effective stress. Thus, PDP behaviour can be defined by PDL. In this paper, we show how combined analyses, using typically collected field data, can be used to better define and constrain the modelling of PDP. We illustrate this process based on a well case study that includes the following data: fracture fabric and porosity reasonably defined from image log and areal core studies; DFIT data acquired under initial saturation conditions; hydraulic fracturing data; and longer term production data. These analyses will be integrated and used to constrain the parameters required to obtain a rate and pressure history-match from the post-frac well production data. This workflow has application in other coal seam gas cases by identifying key variables where hydraulic fracturing performance has been unable to overcome limitations based on pressure or stress dependent behaviours and often accompanied by low reservoir permeability values. While this is purposely targeting areas where only typically collected field data is available, this workflow can include coal testing data for matrix swelling/shrinkage properties or other production data analysis techniques.

Introducción: el linfoma B difuso de célula grande (LBDCG) doble o triple expresor es un raro grupo de linfomas caracterizado por expresión simultáneade C-MYC y BCL-2 y/o BCL-6 en tinciones de inmunohistoquímica (IHQ). Este patrón de expresión es considerado un marcador de mal pronóstico, aunque no de la misma magnitud que las translocaciones de C-MYC y BCL-2 y/o BCL-6 detectadas por hibridación fluorescente in situ (FISH) en los linfomas B de alto grado doble o triple golpe (LBAG-DG/TG). Existe escasa literatura que describa el comportamiento del LBDCG doble o triple expresor en nuestro medio o estudios que describan métodos para identificar pacientes con linfomas agresivos en quienes deba realizarse FISH para detectar translocaciones de C-MYC y BCL-2 y BCL-6 con el fin de diagnosticar LBAG-DG/TG. Materiales y métodos: llevamos a cabo un estudio retrospectivo observacional en pacientes con diagnóstico inicial de linfoma B difuso de célula grande (LBDCG) con doble o triple expresión de C-MYC, BCL-2 y/o BCL-6 y con resultados de FISH para C-MYC, BCL-2 y BCL-6 disponibles.

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