Determination of the Near-Wellbore Pressure Drop for Dual Casing in Hydraulic Fracturing and Refracturing Applications

Due to the increases in completion costs demand for production improvements, fracturing through double casing in upper reservoirs for mature wells and refracturing early stimulated wells to change the completion design, has become more and more popular. One of the most common technologies used to re-stimulate previously fracked wells, is to run a second, smaller casing or tubular inside of the existing and already perforated pipes of the completed well. The new inner and old outer casing are isolated from each other by a cement layer, which prevents any hydraulic communication between the pre-existing and new perforations, as well as between adjacent new perforations. For these smaller inner casing diameters, specially tailored and designed re-fracturing perforation systems are deployed, which can shoot casing entrance holes of very similar size through both casings, nearly independent of the phasing and still capable of creating tunnels reaching beyond the cement layer into the natural rock formation. Although discussing on the API RP-19B section VII test format has recently been initiated and many companies have started to test multiple casing scenarios and charge performance, not much is known about the complex flow through two radially aligned holes in dual casings. In the paper we will look in detail at the parameters which influence the flow, especially the Coefficient of Discharge of such a dual casing setup. We will evaluate how much the near wellbore pressure drop is affected by the hole's sizes in the first and second casing, respectively the difference between them and investigate how the cement layer is influenced by turbulences, which might build up in the annulus. The results will enhance the design and provide a better understanding of fracturing or refracturing through double casings for hydraulic fracturing specialists and both operation and services companies.

BALLCOURT REPRESENTATIONS IN QUIECHAPA, OAXACA, MEXICO: RITUAL OFFERING, FERTILITY, AND LIFE

During an archaeological survey in the municipality of San Pedro Mártir Quiechapa, Oaxaca, Mexico, archaeologists from the Proyecto Arqueológico de Quiechapa (PAQuie) encountered and documented a number of carved stone elements. Of particular interest are the 30 representations of ballcourts carved into natural rock outcrops at two sites in the region. This is the highest density in which this type of ballcourt representation occurs throughout Mesoamerica. After their initial discovery, members of PAQuie documented the carved stone ballcourts using structure-from-motion (SfM) photogrammetry, a quick and affordable technique to collect 3D spatial, quantitative, and visual data of stone carvings. In this article, I report on the carved stone ballcourt representations documented in the Quiechapa region and offer some preliminary interpretations. I first provide some description of the broader archaeological context in which the carvings were found. Then I describe the methods used to record the stone carvings, followed by a presentation of the data. Finally, in dialogue with extant literature, I explore some possibilities as to why these carved stone ballcourt representations were created, how they may have been used, and what they may symbolize.

Y-Mat: an improved hybrid finite-discrete element code for addressing geotechnical and geological engineering problems

PurposeContinua and discontinua coexist in natural rock materials. This paper aims to present an improved approach for addressing the mechanical response of rock masses based on the combined finite-discrete element method (FDEM) proposed by Munjiza.Design/methodology/approachSeveral algorithms have been programmed in the new approach. The algorithms include (1) a simpler and more efficient algorithm to calculate the contact force; (2) An algorithm for tangential contact force closer to the actual physical process; (3) a plastic yielding criterion (e.g. Mohr-Coulomb) to modify the elastic stress for fitting the mechanical behavior of elastoplastic materials; and (4) a complete code for the mechanical calculation to be implemented in Matrix Laboratory (MATLAB).FindingsThree case studies, including two standard laboratory experiments (uniaxial compression and Brazilian split test) and one engineering-scale anti-dip slop model, are presented to illustrate the feasibility of the Y-Mat code and its ability to deal with multi-scale rock mechanics problems. The results, including the progressive failure process, failure mode and trajectory of each case, are acceptable compared to other corresponding studies. It is shown that, the code is capable of modeling geotechnical and geological engineering problems.Originality/valueThis article gives an improved FDEM-based numerical calculation code. And, feasibility of the code is verified through three cases. It can effectively solve the geotechnical and geological engineering problems.

Impact of Safe Rock® Minerals, Mineral Fertilizers, and Manure on the Quantity and Quality of the Wheat Yield in the Rice–Wheat Cropping System

Rice–wheat (RW) rotation is the largest agriculture production system in South Asia with a multifaceted role in maintaining the livelihood of people. The customary practices and indiscriminate use of synthetic fertilizers have culminated in the decline of its productivity and profitability during the past two decades, thus affecting the sustainability of wheat. Safe Rock® Minerals (SRM) is a multi-nutrient rich natural rock mineral with great potential to manage soil degradation, reducing the input of fertilizers, improving soil fertility, and plant health. Thus, a field trial was conducted at the research farm of ICAR—Indian Agricultural Research Institute, New Delhi from 2016 to 2018 to evaluate the impact of Safe Rock® Minerals (SRM) on biometric parameters, productivity, quality, and nutrient uptake by conventional wheat and System of Wheat Intensification (SWI) in the wheat–rice cropping system. The results indicate that SWI performed better in terms of growth, yield, and quality parameters than conventional wheat. Among nutrient management practices; the highest growth, yield, and yield attributes of wheat were achieved with the use of SRM application 250 kg ha−1 + 100% Recommended Dose of Fertilizer (RDF). SRM application also increased grain protein content significantly. In conclusion, the integrated use of SRM with organic manures can serve as an eco-friendly approach for sustainable wheat production.

Arc-parallel shears in collisional orogens: Global review and paleostress analyses from the NW Lesser Himalayan Sequence (Garhwal region, Uttarakhand, India)

Interest in hydrocarbon exploration from the the Lesser Himalayan Sequence (LHS) has recently been revived amongst petroleum geoscientists. Understanding the paleostress regime and the deformation processes are the two important steps to understand the structural geology of any (petroliferous) terrane. Arc-parallel shear is an integral deformation process in orogeny. The scale of the consequent deformation features can range from micro-mm up to regional scale. Unlike orogen-perpendicular shear, different driving forces can produce orogen-parallel shears. We review these mechanisms/theories from several orogens including the Himalaya and compile 44 locations worldwide with reported orogen-parallel shear. Due to continuous crustal shortening by the India-Eurasia collision, the squeezed rock mass at the plate interface has produced the Himalayan Mountain chain. In addition, the rock mass also escapes laterally along the orogenic trend. Tectonic stress-field governs this mass flow. Field study and microstructural analysis in the northwest LHS (India) reveals orogen-parallel brittle and ductile shear movement. Y- and P- brittle shear planes, and the S- and C- ductile shear planes reveal the following shears documented on the ~ NW-SE trending natural rock selections: (i) top-to-NW up, (ii) top-to-SE up, (iii) top-to-NW down, and (iv) top-to-SE down. Our paleostress analysis indicates top-to-SE down and top-to-NW down shears occurred due to stretching along ~ 131°-311° (Dext), whereas top-to-SE up and top-to-NW up shear fabric originated due to shortening along ~133.5°-313.5° (Dcompr). Previous authors considered that the orogen-parallel extension generated ~ 15-5 Ma due to vertical thinning of the Himalaya. The NE-trending Delhi-Haridwar Ridge below the LHS plausibly acted as a barrier to the flowing mass and piled up the rock mass in the form of NW-SE/orogen-parallel compression. The NW-SE compression can be correlated with the D3 of Hintersberger et al. (2011) during ~ 4-7 Ma.

Thermoluminescence Sensitization of Phyllite Natural Rock

A sensitization procedure is used to enhance the thermoluminescence (TL) sensitivity of phyllite to emit radiation. Phyllite is a type of foliated metamorphic rock made from slate. This study examines naturally grown phyllite rock, which had not been previously studied. Using a Thermo 3500 manual reader, the TL sensitivity of phyllite as a function of dosage was measured. The doses required to perform this study were administered using a 60Co source. The statistical regression test of the data had a significance level of p < 0.05. The study also included thermal and pre-dose effects. Using the sensitization procedure, the nonlinearity in TL dose–response was removed, and the sensitivity was increased 44 times that of its original value. The fading study showed a dependence on the test dose. According to the obtained results, the combination of linear dose–response and high sensitivity to gamma radiation makes phyllite an important rock for dating and retrospective dosimetry.

Molluscs community as a keystone group for assessing the impact of urban sprawl at intertidal ecosystems

Mollusc communities are getting endangered in the aftermath of urban sprawl because artificial structures do not surrogate natural substrates. In this study, we compared the diversity, community and trophic arrangements of molluscs among different models of artificial substrate and their adjacent natural rock, to detect relationships between some abiotic variables and the mollusc communities. Complexity, chemical composition and age were tested as potential drivers of the community. Diversity, community and trophic structure differed between natural and artificial substrates. Complexity at the scale of cm was detected as the most important factor driving the community structure. In addition, a chemical composition based on silica and/or scarce calcium carbonates seems to be relevant for molluscs, as well as for the secondary substrate where they inhabit. However, age did not seem to be a driving factor. Among the different artificial structures, macroscale complexity was detected as the main factor diverging a drastically poor community at seawall from other artificial structures. In this context, macro and microscale complexity, chemical composition and mineral type are variables to consider in future designs of artificial substrates.

Grain size distribution of waste rock masses of Kuzbass coal strip mines

Grain size distribution as a structural characteristic of waste rock and bulk masses in the course of mining and construction works acquires quantitative values in the process of rock blasting and hauling of rock mass. Such physical-mechanical and structural-textural parameters of a rock mass, as the ultimate strength of rocks and rock mass, fracturing, diameter of the natural rock jointing, have a significant impact on the blasted rock mass grain size distribution. On the other hand, such characteristics as stability, permeability of waste rock masses largely depend on the lithology and grain size distribution of the loosened rocks composing waste rock dumps and their height distribution within a dump. The paper describes the findings of the study of the grain size distribution of waste rock masses of Kuzbass coal strip mines and the features of its spatial variations within the masses. The textures of the bulk masses and physical and technical properties of the stacked rocks were studied both at the Kuzbass waste rock sites and in laboratory conditions. The grain size distribution of the fine lump part of the dumps with the lump size up to 50 mm was investigated by sieve method according to GOST 12536–2014, and the medium and large lump part was studied using oblique photoplanimetry. The field observations showed that the bottom part of the rock dumps, dumped by peripheral bulldozer or excavator methods was composed of coarse fraction with average lump size of: d_cr = 0.8–1 m, while the middle part, of rock lumps of d_cr = 0.4–0.6 m, and the upper part, mainly of fine fraction with lump size of less than 0.1 m. The ratio of length, width, and thickness of the blasted rock lumps was 1:0.85:0.8, which corresponds to elongated-flattened shape of the lumps. This requires significant number of coordinates for describing the lump positions in the rock mass, as well as taking into account the moments of inertia when modeling the motion of such lumps until they reach a stable position. Up-to-date non-commercial or commercial software and corresponding hardware can be used to take into account non-isometric shape of the lumps when modeling their motion.

Influence of Waste Cork with Thinner on the Rheological Properties of Asphalt

Over the last two decades, the rapid and continued deterioration of the transportation network has been regarded as a major issue. There are many measures that can be taken to reduce this deterioration and improve road specifications, including improving road design, using higher quality materials, and using more efficient construction methods. This study is concerned with three principles: including investigating the impact of using waste paste on the rheological properties of bitumen; the environmental pollution that is a global problem; and the economic benefits as a result of the reusing of waste materials such as corks to produce new reusable materials like Modified-Asphalt. In this research, cork has been melted by thinner and mixed with asphalt to get a good paste with weight percentages of 1%, 3%, 5%, and 7%. After conducting the necessary tests on the samples, it was found that the addition of waste paste to virgin bitumen has softened the bitumen by decreasing the hardness and adhesiveness of the bitumen by increasing penetration with increasing cork paste content. The findings show that the current procedure can be used in cold regions because it requires less hard asphalt than that used in hot regions. It can also be used with natural asphalt, like natural rock asphalt, in various percent to give asphalt with suitable properties for use in roofing and paving roads.