Novel Sandstone Stimulation Using Thermochemical Fluid: Successful Field Application

2021 ◽  
Author(s):  
Amjed Mohammed Hassan ◽  
Ayman Raja Al-Nakhli ◽  
Mohamed Ahmed Mahmoud
Keyword(s):  
Injection Rate ◽  
Field Application ◽  
New Technique ◽  
Compatibility Study ◽  
Tight Sandstone ◽  
Rock Permeability ◽  
Before And After ◽  
Reservoir Conditions ◽  
Well Injectivity

Abstract Sandstone acidizing is implemented to remove the damage from the near-wellbore region. Different techniques are used to remove the formation and damage and improve reservoir productivity. This paper presents a novel sandstone stimulation technique using thermochemical fluids. The used chemicals are not reactive at surface conditions and react only at the downhole conditions. The reservoir temperature or pH controller can be used to activate the chemical reaction. A successful field application of the proposed method is reported in this paper. Different measurements were conducted to assess the performance of the new technique. A compatibility study was conducted at different conditions to evaluate the generation of acid foam. Also, Coreflood experiments were performed by injecting the foam generating solutions into tight sandstone cores. The rock permeability and the pores network were evaluated before and after the chemical injection. Scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) and analyses were performed. Moreover, a field application of the in situ acid foam generation was conducted. The treatment was implemented by injecting the solutions to react at the downhole conditions and improve the well injectivity. The profiles of injection rate, circulation pressure, and total volume were monitored during the field treatment to assess the treatment performance. Results showed that the used solutions can generate foam in less time and the volume of the generated foam is around 30 folds of the original chemical volumes. The in situ generated foam can penetrate deeper in the reservoir due to the larger foam volume compared to original chemicals, leading to improve treatment efficiency. Also, the new technique increased the rock permeability from 0.6 to 420 mD due to the dissolution and removal of illite minerals as well as the generation of micro-fractures due to the pressure pulses. The field application showed a very successful performance and the well injectivity was increased by 18 times after the treatment. The proposed technique utilizes thermochemical fluids to generate acid foam at the reservoir conditions. This technique can eliminate all the risks associated with HSE concerns, in addition to the corrosion issues. Also, the proposed treatment showed a successful field application and increased the well injectivity up by 18 folds of the original injectivity.

An Innovative Acid Diversion Using In-Situ Foam Generation: Experimental and Successful Field Application

2021 ◽  
Author(s):  
Ayman Al-Nakhli ◽  
Mohannad Gizani ◽  
Abdualilah Baiz ◽  
Mohammed Yami
Keyword(s):  
Horizontal Wells ◽  
Field Application ◽  
Damage Potential ◽  
Left Behind ◽  
Foam Generation ◽  
Water Breakthrough ◽  
Acid Diversion ◽  
Well Injectivity ◽  
Pressure Resistance

Abstract In carbonate reservoirs, effective acid stimulation is essential to overcome reservoir damage and mainline high oil production. Recently, most of oil wells are being drilled horizontally to maximize production. Acid stimulation of horizontal wells with long intervals require very effective acid diversion system. If the diversion system is not efficient enough, most of the acid will be leaking-off near the casing shoe, in openhole well, which will result in a fast water breakthrough and diminish production. This study describes a breakthrough treatment for acidizing long horizontal wells in carbonate formations. The novel technology is based on in-situ foam generation to divert the acid. Gas diversion, as a foam, is a perfect diversion mechanism as gas creates pressure resistance which forces the acid stages to be diverted to new ones?. The diversion will not require the acid to be spent, compared to viscoelastic diverting system. Moreover, no gel is left behind post treatment, which will eliminate any damage potential. The system is not impacted with the presence of corrosion products, where diverting system will not function without effective pickling and tubular cleanup. Lab results showed that the new in-situ foam generation system was very effective on both dolomite and calcite cores. The system creates high back pressure when foam is generated, which significantly diverts the acid stages to stimulate other intervals. Moreover, the new system minimizes acid leak-off and penetration. Open completing the job, the foam collapse leaving no left behind any damaging material. Field application of the in-situ foam generating system showed high success rate and outperformed other diversion mechanisms. The well gain was up to 18 folds of the original well injectivity.

scholarly journals Study on Propagation Behaviors of Hydraulic Fracture Network in Tight Sandstone Formation with Closed Cemented Natural Fractures

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-22
Author(s):  
Jun Zhang ◽  
Yu-Wei Li ◽  
Wei Li ◽  
Zi-Jie Chen ◽  
Yuan Zhao ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fracture Network ◽  
In Situ Stress ◽  
Injection Rate ◽  
Fluid Viscosity ◽  
Tight Sandstone ◽  
Propagation Behavior ◽  
Sandstone Formation

Natural fractures in tight sandstone formation play a significant role in fracture network generation during hydraulic fracturing. This work presents an experimental model of tight sandstone with closed cemented preexisting fractures. The influence of closed cemented fractures’ (CCF) directions on the propagation behavior of hydraulic fracture (HF) is studied based on the hydraulic fracturing experiment. A field-scaled numerical model used to simulate the propagation of HF is established based on the flow-stress-damage (FSD) coupled method. This model contains the discrete fracture network (DFN) generated by the Monte-Carlo method and is used to investigate the effects of CCFs’ distribution, CCFs’ strength, and in-situ stress anisotropy, injection rate, and fluid viscosity on the propagation behavior of fracture network. The results show that the distribution direction of CCFs is critical for the formation of complex HFs. When the angle between the horizontal maximum principal stress direction and the CCFs is in the range of 30° to 60°, the HF network is the most complex. There are many kinds of compound fracture propagation patterns, such as crossing, branching, and deflection. The increase of CCFs’ strength is not conducive to the generation of branched and deflected fractures. When the in-situ stress difference ranges from 3 MPa to 6 MPa, the HF network’s complexity and propagation range can be guaranteed simultaneously. The increase in the injection rate will promote the formation of the complex HF network. The proper increase of fracturing fluid viscosity can promote HF’s propagation. However, when the viscosity is too high, the complex HFs only appear around the wellbore. The research results can provide new insights for the hydraulic fracturing optimization design of naturally fractured tight sandstone formation.

Real-life Field Studies of the NOx Removing Properties of Photocatalytic Surfaces in Roskilde and Copenhagen Airport, Denmark

2020 ◽  
Vol 01 ◽  
Author(s):  
Henrik Jensen ◽  
Pernille D. Pedersen
Keyword(s):  
Air Quality ◽  
High Stability ◽  
Reference Site ◽  
Real Life ◽  
Field Studies ◽  
The Real ◽  
Before And After ◽  
Parking Lot ◽  
Photocatalytic Concrete

Aims: To evaluate the real-life effect of photocatalytic surfaces on the air quality at two test-sites in Denmark. Background: Poor air quality is today one of the largest environmental issues, due to the adverse effects on human health associated with high levels of air pollution, including respiratory issues, cardiovascular disease (CVD), and lung cancer. NOx removal by TiO2 based photocatalysis is a tool to improve air quality locally in areas where people are exposed. Methods: Two test sites were constructed in Roskilde and Copenhage airport. In Roskilde, the existing asphalt at two parking lots was treated with TiO2 containing liquid and an in-situ ISO 22197-1 test setup was developed to enable in-situ evaluation of the activity of the asphalt. In CPH airport, photocatalytic concrete tiles were installed at the "kiss and fly" parking lot, and NOx levels were continuously monitored in 0.5 m by CLD at the active site and a comparable reference site before and after installation for a period of 2 years. Results: The Roskilde showed high stability of the photocatalytic coating with the activity being largely unchanged over a period of 2 years. The CPH airport study showed that the average NOx levels were decreased by 12 % comparing the before and after NOx concentrations at the active and reference site. Conclusion: The joined results of the two Danish demonstration projects illustrate a high stability of the photocatalytic coating as well as a high potential for improvements of the real-life air quality in polluted areas.

scholarly journals Nanocomposites of Polyaniline and Cellulose Nanocrystals Prepared in Lyotropic Chiral Nematic Liquid Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Dawei Zhang ◽  
Lihong Zhang ◽  
Bingzhe Wang ◽  
Guangzhe Piao
Keyword(s):  
Liquid Crystals ◽  
Cellulose Nanocrystals ◽  
Nematic Liquid Crystals ◽  
Weight Ratio ◽  
Asymmetric Reaction ◽  
Reaction Field ◽  
Electron Microscopies ◽  
Chiral Nematic ◽  
Before And After

Stable lyotropic chiral nematic liquid crystals (N*-LCs) of cellulose nanocrystals (CNs) were prepared via hydrolysis using sulfuric acid. The lyotropic N*-LCs were used as an asymmetric reaction field to synthesize polyaniline (PANI) onto CNs by in situ polymerization. As a primary step, we examined the mesophase transition of the N*-LCs of CNs suspension before and after in situ polymerization of aniline (ANI) by polarizing optical microscopy. The structure of nanocomposites of PANI/CNs was investigated at a microscopic level using Fourier transform infrared spectroscopy and X-ray diffraction. Influence of the CNs-to-ANI ratio on the morphology of the nanocomposites was also investigated at macroscopic level by scanning electron and transmission electron microscopies. It is found that the weight ratio of CNs to aniline in the suspension significantly influenced the size of the PANI particles and interaction between CNs and PANI. Moreover, electrical properties of the obtained PANI/CNs films were studied using standard four-probe technique. It is expected that the lyotropic N*-LCs of CNs might be available for an asymmetric reaction field to produce novel composites of conjugated materials.

Assessment on the Transport of Polymeric Solution through High-Salinity Reservoirs Containing Divalent Cations

2013 ◽  
Vol 807-809 ◽  
pp. 2607-2611
Author(s):  
Byung In Choi ◽  
Moon Sik Jeong ◽  
Kun Sang Lee
Keyword(s):  
Quantitative Assessment ◽  
High Salinity ◽  
Divalent Cations ◽  
Polymer Concentration ◽  
Field Application ◽  
Polymer Flooding ◽  
Sweep Efficiency ◽  
Chemical Theory ◽  
Bottom Hole ◽  
Reservoir Conditions

Water salinity and hardness have been regarded as main limitation for field application of polymer floods. It causes not only reduction of polymer concentration, but also injectivity loss in the near wellbore. Based on the mathematical and chemical theory, extensive numerical simulations were conducted to investigate performance of polymer floods in the high-salinity reservoirs. According to results from simulations, the high salinity reduces the viscosity of polymer in contacting area. That causes a poor sweep efficiency of polymer flooding. Moreover, the presence of divalent cations makes the project of polymer flooding worse. That is because of excessively increased bottom-hole pressure in injection well by the precipitation of polymer. The quantitative assessment of polymer floods needs to be required before field application. Therefore, the results in this paper are helpful for optimal polymer flooding design under harsh reservoir conditions.

In-Situ SEM Observations of Moving Interfaces during Recrystallisation

2006 ◽  
Vol 519-521 ◽  
pp. 1341-1348 ◽  
Author(s):  
Sybrand van der Zwaag ◽  
E. Anselmino ◽  
A. Miroux ◽  
David J. Prior
Keyword(s):  
Grain Boundaries ◽  
Small Groups ◽  
Detailed Understanding ◽  
Small Areas ◽  
Orientation Contrast ◽  
Moving Interfaces ◽  
Innovative Method ◽  
Before And After ◽  
In Situ Observations

To obtain further progress and a more detailed understanding of the mechanisms involved in recrystallisation, new and more accurate techniques such as in-situ observations are necessary. This innovative method has been used to monitor the recrystallisation process in a FEGSEM equipped with hot stage. Observations are done in backscatter mode with particular attention to orientation contrast. EBSD maps of the observed areas can be acquired before and after recrystallisation. Details of the movement of the interfaces between the recrystallised region and the parent structure are recorded and analysed. The results show that the grain boundaries observed do not move smoothly but with a jerky motion. The recrystallising front sweeps through small areas, corresponding to single sub-grains or small groups of them, very rapidly and then stops at other sub-grain boundaries for varying time before progressing to the following area.

Experiment on Mechanical Properties and Seepage Capability of Deep Tight Sandstone Under True-Triaxial Stresses Environment

2021 ◽  
Author(s):  
Jiaying Li ◽  
Chunyan Qi ◽  
Ye Gu ◽  
Yu Ye ◽  
Jie Zhao
Keyword(s):  
Mechanical Properties ◽  
In Situ Stress ◽  
Stress Sensitivity ◽  
Stress Conditions ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
True Triaxial ◽  
Strain Behavior ◽  
Triaxial Stresses

Abstract The characteristics of seepage capability and rock strain during reservoir depletion are important for reservoir recovery, which would significantly influence production strategy optimization. The Cretaceous deep natural gas reservoirs in Keshen Gasfield in Tarim Basin are mainly buried over 5000 m, featuring with ultra-low permeability, developed natural fractures and complex in-situ stress states. However, there is no comprehensive study on the variation of mechanical properties and seepage capability of this gas reservoir under in-situ stress conditions and most studies on stress-sensitivity are conducted under conventional triaxial or uniaxial stress conditions, which cannot truly represent in-situ stress environment. In this work, Cretaceous tight sandstone in Keshen Gasfield was tested under true-triaxial stresses conditions by an advanced geophysical imaging true-triaxial testing system to study the stress-sensitivity and anisotropy of rock stress-strain behavior, porosity and permeability. Four groups of sandstone samples are prepared as the size of 80mm×80mm×80mm, three of which are artificially fractured with different angle (0°,15°，30°) to simulate hydraulic fracturing. The test results corresponding to different samples are compared to further reveal the influence of the fracture angle on rock mechanical properties and seepage capability. The samples are in elastic strain during reservoir depletion, showing an apparent correlation with fracture angles. The porosity decreases linearly with stress loading, where the decrease rate of effective porosity of fracture samples is significantly higher than that of intact samples. The permeabilities decrease exponentially and show significant anisotropy in different principal stress directions, especially in σH direction. The mechanical properties and seepage capability of deep tight sandstone are successfully tested under true-triaxial stresses conditions in this work, which reveals the stress-sensitivity of anisotropic permeability, porosity and stress-strain behavior during gas production. The testing results proposed in this paper provides an innovative method to analyse rock mechanical and petrophysical properties and has profound significance on exploration and development of tight gas reservoir.

A New Technique to Predict In Situ Stress Increment Due to Biowaste Slurry Injection Into a Sandstone Formation

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Sherif M. Kholy ◽  
Ahmed G. Almetwally ◽  
Ibrahim M. Mohamed ◽  
Mehdi Loloi ◽  
Ahmed Abou-Sayed ◽  
...  
Keyword(s):  
Function Analysis ◽  
Injection Pressure ◽  
In Situ Stress ◽  
New Technique ◽  
Strong Impact ◽  
Stress Increment ◽  
Injection Zone ◽  
Fracture Closure ◽  
Slurry Injection

Underground injection of slurry in cycles with shut-in periods allows fracture closure and pressure dissipation which in turn prevents pressure accumulation and injection pressure increase from batch to batch. However, in many cases, the accumulation of solids on the fracture faces slows down the leak off which can delay the fracture closure up to several days. The objective in this study is to develop a new predictive method to monitor the stress increment evolution when well shut-in time between injection batches is not sufficient to allow fracture closure. The new technique predicts the fracture closure pressure from the instantaneous shut-in pressure (ISIP) and the injection formation petrophysical/mechanical properties including porosity, permeability, overburden stress, formation pore pressure, Young's modulus, and Poisson's ratio. Actual injection pressure data from a biosolids injector have been used to validate the new predictive technique. During the early well life, the match between the predicted fracture closure pressure values and those obtained from the G-function analysis was excellent, with an absolute error of less than 1%. In later injection batches, the predicted stress increment profile shows a clear trend consistent with the mechanisms of slurry injection and stress shadow analysis. Furthermore, the work shows that the injection operational parameters such as injection flow rate, injected volume per batch, and the volumetric solids concentration have strong impact on the predicted maximum disposal capacity which is reached when the injection zone in situ stress equalizes the upper barrier stress.

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