Engineering-oriented “sweet spot” prediction for tight sandstone gas reservoirs: A case study from Sulige gas field in Western China

2020 ◽  
Vol 8 (4) ◽  
pp. T813-T821
Author(s):  
Hailiang Li ◽  
Liping Zhang ◽  
Jinyong Gui ◽  
Hailong Wang ◽  
Shengjun Li
Keyword(s):  
Hydraulic Fracturing ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Western China ◽  
Brittleness Index ◽  
Petrophysical Properties ◽  
Sweet Spot ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Field

Tight sandstone gas reservoirs have the characteristics of low porosity and permeability, deep burial, and low production of vertical wells, which are difficult to predict and exploit. Usually, finding a “sweet spot” requires finding zones with well-developed fractures or easy stimulation by hydraulic fracturing in the later stage. For some tight sandstone gas reservoirs where natural fractures are not developed, directional hydraulic fracturing is a good choice to improve single well production. However, not all reservoirs can achieve the desired productivity after hydraulic-fracture stimulation. In the exploration of the Sulige (SLG) gas field in Western China, sweet spots with strong brittleness and good petrophysical properties can ensure the success of hydraulic fracturing. We have evaluated the SLG gas field to determine how to implement an engineering-oriented sweet spot prediction workflow. The method has five steps: data-quality analysis, lithology prediction, brittleness prediction, petrophysical property prediction, and well planning. We evaluated the feasibility of subsequent sensitive elastic parameter inversion by comparing the accrual and simulated seismic gathers. Then, we used a direct inversion method of Young’s modulus to predict lithology and identify fluid at the same time. Next, we constructed a new brittleness index by combining the rate of change of Young’s modulus and the quartz content to evaluate the brittleness of rocks, which can overcome the shortage of the conventional brittleness index constructed by a single parameter. Finally, by using the brittleness index, we combined the petrophysical properties inversion results to select regions with strong brittleness and good petrophysical properties as the basis of well planning. This workflow achieved remarkable results in the exploration of tight sandstone gas reservoirs in the SLG gas field in Western China.

Manuscript Title: Mechanical and Microstructural Studies of Volcanic Ash Beds in Unconventional Reservoirs

2021 ◽  
Author(s):  
Juan C Acosta ◽  
Mark E Curtis ◽  
Carl H Sondergeld ◽  
Chandra S Rai
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Young’S Modulus ◽  
Volcanic Ash ◽  
Young's Modulus ◽  
Microstructural Analysis ◽  
Thin Layers ◽  
Ion Milling ◽  
Eagle Ford ◽  
Diagenetic Alteration

Abstract Volcanic ash beds are thin layers commonly observed in the Eagle Ford, Niobrara and, Vaca Muerta formations. Because of their differences in composition, sedimentary structures, and diagenetic alteration, they exhibit a significant contrast in mechanical properties with respect to surrounding formation layers. This can impact hydraulic fracturing, affecting fracture propagation and fracture geometry. Quantifying the mechanical properties of ash beds becomes significant; however, it is a challenge with traditional testing methods. Common logging fails to identify the ash beds, and core plug testing is not possible because of their friability. In this study, nanoindentation was used to measure the mechanical properties (Young's modulus, creep, and anisotropy) in Eagle Ford ash beds, and to determine the contrast with the formation matrix properties. Two separate ash beds of high clay and plagioclase composition were epoxied in an aluminum tray and left for 48 hours curing time. Horizontal and vertical samples of ash beds were acquired and mounted on a metal stub, followed by polishing and broad beam ion milling. Adjacent samples were also prepared for high-resolution Scanning Electron Microscope (SEM) microstructural analysis. The Young's modulus in ash beds ranged from 12 to 24 GPa, with the horizontal direction Young's modulus being slightly greater than that of the vertical samples. The Young's modulus contrast with adjacent layers was calculated to be 1:2 with clay-rich zones and 1:4 with calcite rich zones. The creep deformation rate was three times higher for ash beds compared to other zones. Using Backus averaging, it was determined that the presence of ash beds can increase the anisotropy in the formation by 15-25%. SEM results showed a variation in microstructure between the ash beds with evidence of diagenetic conversion of rhyolitic material into clays. Key differences between the two ash beds were due to the presence of plagioclase and the occurrence of porosity within kaolinite. Overall porosity varied between the two ash beds and adjacent carbonate layers showing a significant increase in porosity. Understanding the moduli contrast between adjacent layers can improve the hydraulic fracturing design when ash beds are encountered. In addition, the presence of these beds can lead to proppant embedment and loss in fracture connectivity. These results can be used for improving geomechanical models.

scholarly journals Approximate Dynamic Programming Based Control of Proppant Concentration in Hydraulic Fracturing

Mathematics ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 132 ◽  
Author(s):  
Harwinder Singh Sidhu ◽  
Prashanth Siddhamshetty ◽  
Joseph Kwon
Keyword(s):  
Mechanical Properties ◽  
Dynamic Programming ◽  
Hydraulic Fracturing ◽  
Young’S Modulus ◽  
Large Scale ◽  
Approximate Dynamic Programming ◽  
Young's Modulus ◽  
Computational Cost ◽  
Control Technique ◽  
Rock Mechanical Properties

Hydraulic fracturing has played a crucial role in enhancing the extraction of oil and gas from deep underground sources. The two main objectives of hydraulic fracturing are to produce fractures with a desired fracture geometry and to achieve the target proppant concentration inside the fracture. Recently, some efforts have been made to accomplish these objectives by the model predictive control (MPC) theory based on the assumption that the rock mechanical properties such as the Young’s modulus are known and spatially homogenous. However, this approach may not be optimal if there is an uncertainty in the rock mechanical properties. Furthermore, the computational requirements associated with the MPC approach to calculate the control moves at each sampling time can be significantly high when the underlying process dynamics is described by a nonlinear large-scale system. To address these issues, the current work proposes an approximate dynamic programming (ADP) based approach for the closed-loop control of hydraulic fracturing to achieve the target proppant concentration at the end of pumping. ADP is a model-based control technique which combines a high-fidelity simulation and function approximator to alleviate the “curse-of-dimensionality” associated with the traditional dynamic programming (DP) approach. A series of simulations results is provided to demonstrate the performance of the ADP-based controller in achieving the target proppant concentration at the end of pumping at a fraction of the computational cost required by MPC while handling the uncertainty in the Young’s modulus of the rock formation.

Some challenges in hydraulic fracturing of tight gas reservoirs: an experimental study

2011 ◽  
Vol 51 (1) ◽  
pp. 499 ◽  
Author(s):  
Vamegh Rasouli ◽  
Mohammad Sarmadivaleh ◽  
Amin Nabipour
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Oil And Gas ◽  
Interaction Mechanism ◽  
Natural Fracture ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
True Triaxial ◽  
Rock Types ◽  
Interface Parameters

Hydraulic fracturing is a technique used to enhance production from low quality oil and gas reservoirs. This approach is the key technique specifically in developing unconventional reservoirs, such as tight formations and shale gas. During its propagation, the hydraulic fracture may arrive at different interfaces. The mechanical properties and bounding quality of the interface as well as insitu stresses are among the most significant parameters that determine the interaction mechanism, i.e. whether the hydraulic fracture stops, crosses or experiences an offset upon its arrival at the interface. The interface could be a natural fracture, an interbed, layering or any other weakness feature. In addition to the interface parameters, the rock types of the two sides of the interface may affect the interaction mechanism. To study the interaction mechanism, hydraulic fracturing experiments were conducted using a true triaxial stress cell on two cube samples of 15 cm. Sample I had a sandstone block in the middle surrounded by mortar, whereas in sample II the location of mortar and tight sandstone blocks were changed. The results indicated that besides the effect of the far field stress magnitudes, the heterogeneity of the formation texture and interface properties can have a dominant effect in propagation characteristics of an induced fracture.

A Convenient Technology to Calculate Geomechanical Properties From Drilling Data

2020 ◽  
Author(s):  
Mazeda Tahmeen ◽  
Geir Hareland ◽  
John P. Hayes
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Brittleness Index ◽  
Eagle Ford ◽  
Horizontal Drilling ◽  
Geomechanical Properties ◽  
Drilling Data ◽  
Rock Brittleness

Abstract The multistage hydraulic fracturing is the best practice to stimulate unconventional hydrocarbon reservoirs for optimal production. Recent studies suggested that selective stimulation design could significantly increase production rates at a reduced cost rather than using non-selective geometric stages. An optimal design needs detailed logging and core information to selectively perforate and optimize the stimulation treatment. In most cases, the non-selective evenly spaced geometric stimulation design is used, primarily due to the time consuming and expensive conventional logging tools and techniques. In this article, a 3D wellbore friction model is used to estimate the effective downhole weight on bit (DWOB) from the drilling data, directional survey data and drill string information. The estimated DWOB is used as an input to the inverted rate of penetration (ROP) model along with other drilling data, drill bit specifications and reservoir specific formation constants, to calculate rock mechanical and reservoir properties including, compressive strength, Young’s modulus, porosity, permeability and Poisson’s ratio without the use of expensive downhole logging tools. The rock brittleness index is calculated from the relationship between Young’s modulus and Poisson’s ratio based on the definitions of rock brittleness used in recent years. The field data from horizontal drilling of three sample wells were used to investigate the geomechanical properties in the Montney shale formation and the lower Eagle Ford formation in North America. The calculated geomechanical properties were compared to the corresponding test analysis on cores. The authors investigated the rock brittleness index from the sample well data drilled horizontally in the lower Eagle Ford formation. This novel technology could help geologists and reservoir engineers better exploit unconventional reservoirs leading to optimal selective stimulations and greater net present value (NPV).

scholarly journals Modifying the dissolved-in-water type natural gas field simulation model based on the distribution of estimated Young's modulus for the Kujukuri region, Japan

2015 ◽  
Vol 372 ◽  
pp. 417-419
Author(s):  
T. Nakagawa ◽  
R. Matsuyama ◽  
M. Adachi ◽  
S. Kuroshima ◽  
T. Ogatsu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Simulation Model ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Water Type ◽  
Gas Field ◽  
The North ◽  
Chiba Prefecture ◽  
Field Simulation ◽  
Yield Value

Abstract. A simulation model, which covers the part of Southern-Kanto natural gas field in Chiba prefecture, was developed to perform studies and make predictions of land subsidence. However, because large differences between simulated and measured subsidence occurred in the northern modeled area of the gas field, the model was modified with an estimated Young's modulus distribution. This distribution was estimated by the yield value distribution and the correlation of yield value with Young's modulus. Consequently, the simulated subsidence in the north area was improved to some extent.

A New Method to Predict Favorable Gas-Rich Area in Tight Sandstone Gas Reservoir in Daniudi Area

2013 ◽  
Vol 295-298 ◽  
pp. 3328-3332
Author(s):  
Hai Ying Han ◽  
Zhi Zhang Wang ◽  
Xin Xiao Sun ◽  
Wei Jun Wang
Keyword(s):  
Ordos Basin ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Gas Field ◽  
High Productivity ◽  
Integrated Method ◽  
Geological Information ◽  
Sedimentary Microfacies ◽  
Developing Area

Daniudi gas field is a tight sandstone gas field in the northeast of Ordos Basin. How to use the successful experience in developing area to predict favorable gas-rich area in other areas in this gas field is very important to the next exploration and development in this field. This paper proposes a multi-information integrated method to predict favorable gas-rich area. Firstly describe sedimentary microfacies by integrating seismic, logging and geological information; and then summarize and analyze the seismic reflection patterns of medium-high productivity wells; finally determine the favorable gas-rich area with the distribution of storage coefficient based on the previous analysis. The welltest of newly drilled wells shows that the coincidence rate of favorable gas-rich area predicted by this method could be up to 90%,and this method could be extended to use in the other tight sandstone gas reservoirs.

The Characteristics of Tight Gas Reservoirs Microscopic Pore Structure - To Sulige Gas Field as an Example

2015 ◽  
Vol 1092-1093 ◽  
pp. 1485-1489 ◽  
Author(s):  
Jun Sheng ◽  
Wei Sun ◽  
Ji Lei Qin ◽  
Shi Guo Liu ◽  
Ai Ju Li ◽  
...  
Keyword(s):  
Pore Structure ◽  
Physical Characteristics ◽  
Tight Gas ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Field ◽  
Tight Gas Reservoirs ◽  
Constant Rate ◽  
Sandstone Reservoir ◽  
The Impact

The research is based on conventional microscope experiments, the characteristics of microscopic pore structure of tight sandstone reservoir were analyzed via the constant-rate mercury experiment. This paper selected samples of tight sandstone are from the Southeast area of Erdos basin Sulige gas field. The results showed that the dissolution pore and the intergranular pore were mainly reservoir pore structure types; the bundle throat and the lamellar throat were mainly types of throat in the study area. The mainly configure relations of the pore and throat in this area were big pore - fine / fine throat. Finally, according to constant-rate mercury results, analyzed the impact of pore and throats for percolation capacity respectively, came to the conclusions that the tight sandstone gas reservoirs percolation capability in study area is mainly affected by the throat, and the development degree of the throat determines the final physical characteristics of the reservoir.

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