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Mudcake effects on wellbore stress and fracture initiation pressure and implications for wellbore strengthening

Fig. 1 Schematic of the cross section of wellbore, mudcake, and formation (not to scale)

Numerical examples are provided to illustrate the effects of these mudcake parameters. The results show that a low-permeability mudcake enhances FIP, mainly through restricting fluid seepage and pore pressure increase in the near-wellbore region, rather than by mudcake strength. Fluid loss pressure (FLP) should be distinguished from FIP when a

Preparation and application of melamine cross-linked poly ammonium as shale inhibitor

Fig. 3 The appearance of mud balls immersed in different treatment solutions for 12 h. a Distilled water, b 0.8% DEM-8, c 1.0% KCl, d 0.8% DEM-8 + 1.0% KCl

The inhibition mechanism of DEM-8 was studied by thermogravimetric analysis and scanning electron microscope. The results demonstrate that DEM-8 can be adsorbed on clay surface through electrostatic interaction and hydrogen bonds by an anchoring effect and a hydrophobic effect. Introduction Shale oil/gas has been one of the technologies highlighted in the world

Thermogravimetry as a tool for measuring of fracturing fluid absorption in shales

Fig. 6 Comparison of absorbance capacity of the examined samples. Explanations: 0—blank test—fresh sample, W—distilled water saturated, F—the same sample saturated with fracturing fluid, F2—fresh sample saturated with fracturing fluid

In case of rocks which are drilled from the borehole, obtaining such large samples is very difficult; therefore, an attempt was made to determine the rock absorption on small samples, using the TG analysis. Thermogravimetric (TG/DTG) experiments were conducted in temperature range 40–300 °C in synthetic air environment. Shale rock

Cationic surfactant (CTAB) a multipurpose additive in polymer-based drilling fluids

Fig. 1 FTIR spectrum of CTAB

Addition of cetyltrimethylammoniumbromide increased fluid retention capacity of the fluid even at very low concentration 0.1%(w/v) without affecting the mud properties. Also it is compatible with the commercially available fluid loss preventers like pre-gelatinized starch when used in combination. It also performed well in dissolved oxygen test, suggesting eliminating need

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Fig. 9 Local damage zone under loading point of specimen A, damage in the specimen and distance from the center of the disk.

To incorporate the effects of shale formation heterogeneity in the simulation of crack paths, fracture properties of the specimens are defined as spatially random fields. A computational strategy on the basis of stochastic finite element theory is developed that allows to incorporate the effects of heterogeneity of shale rocks on

Fracking: How far from faults?

Fig. 4 Map showing the epicentre of the fracking-induced earthquake of 2nd August 2011 (PH Event) in relation to the hypothesised fault which slipped and the orientations of the maximum (SHmax) and minimum (SHmin) horizontal stress directions. Adapted from Clarke et al. (2014).

An alternative approach is to use microseismic data to infer the extent of fracture propagation and stress changes. Using published microseismic data from 109 fracking operations and analysis of variance, we find that the empirical risk of detecting microseismicity in shale beyond a horizontal distance of 433 m is 32%

An integrated approach to discretized 3D modeling of geomechanical properties for unconventional mature field appraisal in the western Canadian sedimentary basin

Fig. 4 a Depth structural map from tops, b 3D grid layers, c Location of wells in the study area and d 3D block configuration.

To overcome these challenges, this paper describes an integrated approach for deriving 3D geomechanical models of the reservoir by combining results of 3D geocellular models and basin models. The basin model reconstructs the geologic history (i.e., burial history) of the reservoir by back-stripping it to the original depositional thickness. Through

The Application of a New Neutron Induced Gamma Ray Spectroscopy Tool in Evaluation the Shale Gas in Fuling Shale Gas Field

Shale gas reservoir is characterized by complex lithology with ultra-low porosity and permeability, which brings many challenges in the formation evaluation. Elemental Capture Spectroscopy Sonde (ECS) can be used to measure the elements and get the formation of the mineralogy. LithoScanner is a newly-generated spectroscopy tool, which can be used to measure both inelastic and capture spectra, providing estimation of more elements, including silicon, calcium, iron, sulfur, titanium, gadolinium, aluminum, potassium, sodium, magnesium, manganese, carbon, etc.

The changing lithology and borehole rugosity have little influence on the direct measurement of TOC by LithoScanner. LithoScanner shows great advantage in accuracy when comparing with other methods using triple-combo. The systematic lithology classification method in shale gas reservoir using LithoScanner is correlatable in multi-wells. The brittleness index from mineralogy

A Novel Energy-Efficient Pyrolysis Process: Self-pyrolysis of Oil Shale Triggered by Topochemical Heat in a Horizontal Fixed Bed

Figure 5: Description of the main phenomena occurring during the propagation of the self-pyrolysis front.

The results show that the self-pyrolysis of oil shale can be achieved with the proposed method without any need for external heat. The results also verify that fractured oil shale may be more suitable for underground retorting. Moreover, the gas and liquid products from this method were characterised, and a

Design and hydraulic modeling of pulse grinding bits for horizontal wells

Fig. 1. Schematic diagram of a Helmholtz pulse grinding bit. Note: 1. Internal grinding chamber; 2. Accelerating chamber; 3. Mixing chamber; 4. Swabbing chamber; 5. Lower jet channel; 6. Helmholtz oscillation chamber; 7. Diffusion chamber; 8. Internal grinding machine; 9. Throat; 10. Reverse high-speed flow channel.

By using this bit, efficient cuttings removal and rock breaking will be both realized, the chip hold-down effect will be reduced and the cuttings beds in a horizontal well will be also removed. Then, the hydraulic models were established for a pulse generation device, an efficient rock breaking device and

2D Numerical Simulation of Improving Wellbore Stability in Shale Using Nanoparticles Based Drilling Fluid

Figure 24. SEM pictures of the shale. (a) Original shale magnified by 2400 times; (b) Shale contacted with nano-SiO2 in PTT magnified by 2400 times; (c) Original shale magnified by 30,000 times; and (d) Shale contacted with nano-SiO2 in PTT magnified by 30,000 times.

The mechanisms of NP in reducing permeability and stabilizing shale are also discussed. Results showed that fluid filtrate from water-based drilling fluid had a strong tendency to invade the shale matrix and increase the likelihood of wellbore instability in shales. However, the pore fluid pressure near wellbore areas could be

Pore-scale analyses of heterogeneity and representative elementary volume for unconventional shale rocks using statistical tools

Fig. 6 Micro-CT image of Eagle Ford shale rock subsample L1R1N1 at resolution of 6.7 µm and physical extent of 1 mm × 1 mm × 1 mm. Subsample with a segmented three-dimensional CT images showing pores (red), organic matter(turquoise) and minerals (green), e.g. pyrite. b Segmented two-dimensional CT images showing pores (red), organic matter (turquoise) and minerals (green), e.g. pyrite.

In order to analyse the degree of heterogeneity, Eagle Ford parallel sample was further cropped into 96 subsamples. Descriptive statistical approach was then used to evaluate the existence of heterogeneity within the subsamples. Furthermore, the Eagle Ford parallel and perpendicular samples were analysed for volumetric entities representative of the petrophysical

Impact of Stress-Dependent Matrix and Fracture Properties on Shale Gas Production

Unconventional shale gas production is often characterized by a short period of high production followed by a rapid decline in the production rate. Given the high costs of hydraulic fracturing and horizontal drilling, it is critical to identify the mechanisms behind the production loss. The existing shale gas production models often assume constant matrix permeability.

Moreover, the compaction of pore space will also increase the matrix permeability by enhancing the gas-slippage effect. In this paper, a matrix permeability model which couples the effect of pore volume compaction and non-Darcy slip flow is derived. Numerical simulations are conducted to understand the role of matrix permeability evolution

Evaluation of Microseismicity Related to Hydraulic Fracking Operations of Petroleum Reservoirs and Its Possible Environmental Repercussions

Figure 1. Typical microseismic array deployed in vertical well (a) and horizontal well (b).

In addition, the relationship between microseismic magnitude and both depth and injection parameters is examined to delineate the possible framework that controls the system. Generally, microseismicity of typical hydraulic fracturing and injection operations is relatively similar in the majority of basins under investigation and the overall associating seismic energy is

Geometric Heterogeneity of Continental Shale in the Yanchang Formation, Southern Ordos Basin, China

Figure 8 Stratified lamina with various measurements.

These measurement tools correspond to the meter scale, decimeter scale, centimeter scale, millimeter scale and ten-micrometer scale, respectively, with measured thicknesses of 2.26 m, 2.09 dm, 1.70 cm, 1.48 mm and 11.70 μm, respectively. Fractal theory was used to analyze the power exponent distribution of the lamina thickness, with a resulting fractal dimension of 1.06.