Characterize Fracture Development Through Strain Rate Measurements by Distributed Acoustic Sensor DAS

In multistage hydraulic fracturing treatments, the combination of extreme large-scale pumping (high rate and volume) and the high heterogeneity of the formation (because of large contact area) normally results in complex fracture growth that cannot be simply modeled with conventional fracture models. Lack of understanding of the fracturing mechanism makes it difficult to design and optimize hydraulic fracturing treatments. Many monitoring, testing and diagnosis technologies have been applied in the field to describe hydraulic fracture development. Strain rate measured by distributed acoustic sensor (DAS) is one of the tools for fracture monitoring in complex completion scenarios. DAS measures far-field strain rate that can be of assistance for fracture characterization, cross-well fracture interference identification, and well stimulation efficiency evaluation. Many field applications have shown DAS responses on observation wells or surrounding producers when a well in the vicinity is fractured. Modeling and interpreting DAS strain rate responses can help quantitatively map fracture propagation. In this work, a methodology is developed to generate the simulated strain-rate responds to assumed fracture systems. The physical domain contains a treated well that the generate strain variation in the domain because of fracturing, and an observation well that has fiber-optic sensor installed along it to measure the strain rate responses to the fracture propagation. Instead of using a complex fracture model to forward simulate fracture propagation, this work starts from a simple 2D fracture propagation model to provide hypothetical fracture geometries in a relatively reasonable and acceptable range for both single fracture case and multiple fracture case. Displacement discontinuity method (DDM) is formulated to simulate rock deformation and strain rate responds on fiber-optic sensors. At each time step, fracture propagation is first allowed, then stress, displacement and strain field are estimated as the fracture approaches to the observation well. Afterward, the strain rate is calculated as fracture growth to generate patterns as fracture approaching. Extended simulation is conducted to monitor fracture propagation and strain rate responses. The patterns of strain rate responses can be used to recognize fracture development. Examples of strain rate responses for different fracturing conditions are presented in this paper. The relationship of injection rate distribution and strain rate responses is investigated to show the potential of using DAS measurements to diagnose multistage hydraulic fracturing treatments.

Best Practices and Lessons Learned in Deploying and Setting Dissolvable Frac Plugs in Middle East at HPHT Conditions

The multistage hydraulic fracturing technique is considered to be one of the most effective stimulation techniques used for exploiting unconventional plays. The use of dissolvable frac plugs in multistage hydraulic fracturing has the potential to reduce well intervention requirements. Applicability of dissolvable frac plugs, as an integral part of plug and perf operations, in Middle East unconventional plays presents a myriad of technical challenges associated with high-pressure and high-temperature (HPHT) well conditions. Two counteracting drivers coexist in dissolvable frac plug design: 1) The need for the frac plug to withstand well conditions during the entire frac stage operational cycle and 2) the requirement for the frac plug to dissolve as quickly as possible after the stimulation treatment has been placed. The HPHT conditions of the wells utilizing dissolvable frac plugs adds to the complexity of not only the plug design, but also its associated deployment operational procedures. The main premise of the functional methodology of dissolvable frac plugs involves a chain reaction being triggered in the presence of specific fluids under specific temperature conditions. After the commencement of the degradation/dissolution chain reaction process, the useful lifetime of the frac plug begins to deplete, where the degradation chain reaction accelerates with increasing temperature exposure. Site operations will then conform to expedited practices to minimize undesired exposure time. This would minimize the risks of degradation/dissolution before plug setting, plug test, and actual stimulation treatment placement. Based on the HPHT well conditions of Middle Eastern unconventional plays, a structured process was put in place to satisfy the define, assess, select, and execute phases of the initiative The inevitable occurrences of unforeseen complications during operational deployments served to accelerate the learning curve for the continued utilization of dissolvable frac plugs. Operational issues ranging from electric line unit complications to frac pump downtime during the initial frac plug deployments compromised the structural integrity and functionality of the dissolvable frac plugs. Recognizing that exposure time was critical to maintaining the structural integrity of the plug, best practices were derived and enforced to minimize said exposure time. In addition, slight design modifications were made to specific components of the plug to increase its robustness while not compromising the desired degradation rates. The adoption of these mitigating measures has resulted in the acceptance of the dissolvable frac plug as the standard plug option for all plug and perf operations. The vast experience gained during the deployment of more than 1,000 dissolvable frac plugs for hydraulic fracturing stages in a Middle Eastern country has served as a basis to conceive a list of best practices to address mitigating unforeseen complications. These best practices are enforced to minimize plug exposure time, which in turn maximizes the probability of plug utilization success.

Individual Fracture Efficiency Monitoring in Horizontal Wells by Using a New 3d Fine-Grid Temperature Modelling

Profitable development of hard-to-recover reserves often involves drilling of horizontal wells with multistage hydraulic fracturing to increase the oil recovery factor. Usually to monitor the fracture sweep efficiency, pressure transient analysis is used. However, in case of several fractures this method delivers only average hydrodynamic parameters of the well-fracture system. This paper illustrates the value of temperature logging data and demonstrates possibilities of the 3-D thermo-mechanical modelling in evaluating the differential efficiency of multi-stage hydraulic fracturing.

Unlocking Tight Oil: Multistage Horizontal Well Fracturing in Unconventional Reservoir, a Successful UAE Case History

Tight Oil Unconventional Reservoirs are challenging when it comes to development and enhancement of production. Transverse Multistage Hydraulic fracturing technique is widely used to maximize production from unconventional reservoirs, however it can be quite challenging when it comes down to execution across longer Tight Oil Horizontal laterals. The paper describes in full the various aspect of technical and operational planning in order to successfully execute highest number of Frac Stages in a well in UAE across a lateral length of 5300 ft This paper will describe an Integrated Field development Study that included building of Geomechanical Model for in-situ stress characterization and rock elastic properties for 3D Hydraulic Fracture Modelling. The fully 3D Hydraulic Fracture model assisted in geometrically spacing, finalizing and optimizing the number of Frac Stages across the horizontal Lateral. In order to optimize the design, specialized cores studies were conducted as part of the process such as Steady State measurements of permeability. In this paper the testing part will be describe in full and how the study was incorporated in the state-of-art Frac Simulator to ensure optimized frac design and realistic deliverable. The paper focusses on the operation planning, execution and efficiency. This includes frac stages execution, pump down plug and perf, number of cluster optimization & cluster spacing, milling, cleanout and flowback. Also in order to quantify the contribution from each stage, tracer services was utilized which will be detailed in the paper. Finally the paper will also cover the Well Testing strategy, which is one of the crucial aspect of the well deliverability. API Lab and Composition Analysis of Oil & Gas Samples were also conducted post fracturing as part of the study. The overall planning and execution of this well will become a guide and will be utilized for future well and frac design, which will be discussed in the paper. This integrated approach will be utilized in planning and designing future wells. The post fracturing data and production data collected from the well will help in further Frac Stage optimization which will lead to overall cost optimization

The efficiency of gas injection into low-permeability multilayer hydrocarbon reservoirs

The efficiency of gas injection for developing terrigenous deposits within a multilayer producing object is investigated in this article. According to the results of measurements of the 3D hydrodynamic compositional model, an assessment of the oil recovery factor was made. In the studied conditions, re-injection of the associated gas was found to be the most technologically efficient working agent. The factors contributing to the inefficacy of traditional methods of stimulating oil production such as multistage hydraulic fracturing when used to develop low-permeability reservoirs have been analysed. The factors contributing to the inefficiency of traditional oil-production stimulation methods, such as multistage hydraulic fracturing, have been analysed when they are applied to low-permeability reservoirs. The use of a gas of various compositions is found to be more effective as a working agent for reservoirs with permeability less than 0.005 μm2. Ultimately, the selection of an agent for injection into the reservoir should be driven by the criteria that allow assessing the applicability of the method under specific geological and physical conditions. In multilayer production objects, gas injection efficiency is influenced by a number of factors, in addition to displacement, including the ratio of gas volumes, the degree to which pressure is maintained in each reservoir, as well as how the well is operated. With the increase in production rate from 60 to 90 m3 / day during the re-injection of produced hydrocarbon gas, this study found that the oil recovery factor increased from 0.190 to 0.229. The further increase in flow rate to 150 m3 / day, however, led to a faster gas breakthrough, a decrease in the amount of oil produced, and a decrease in the oil recovery factor to 0.19. Based on the results of the research, methods for stimulating the formation of low-permeability reservoirs were ranked based on their efficacy.

The efficiency of gas injection into low-permeability multilayer hydrocarbon reservoirs

The efficiency of gas injection for developing terrigenous deposits within a multilayer producing object is investigated in this article. According to the results of measurements of the 3D hydrodynamic compositional model, an assessment of the oil recovery factor was made. In the studied conditions, re-injection of the associated gas was found to be the most technologically efficient working agent. The factors contributing to the inefficacy of traditional methods of stimulating oil production such as multistage hydraulic fracturing when used to develop low-permeability reservoirs have been analyzed. The factors contributing to the inefficiency of traditional oil-production stimulation methods, such as multistage hydraulic fracturing, have been analysed when they are applied to low-permeability reservoirs. The use of a gas of various compositions is found to be more effective as a working agent for reservoirs with permeability less than 0.005 µm2. Ultimately, the selection of an agent for injection into the reservoir should be driven by the criteria that allow assessing the applicability of the method under specific geological and physical conditions. In multilayer production objects, gas injection efficiency is influenced by a number of factors, in addition to displacement, including the ratio of gas volumes, the degree to which pressure is maintained in each reservoir, as well as how the well is operated. With the increase in production rate from 60 to 90 m3 / day during the re-injection of produced hydrocarbon gas, this study found that the oil recovery factor increased from 0.190 to 0.229. The further increase in flow rate to 150 m3 / day, however, led to a faster gas breakthrough, a decrease in the amount of oil produced, and a decrease in the oil recovery factor to 0.19 Based on the results of the research, methods for stimulating the formation of low-permeability reservoirs were ranked based on their efficacy.

A Case Study of High-Rate Multistage Hydraulic Fracturing in Petrikov Horizon of the Pripyat Trough

Currently, the vast majority of the oil fields of the Republic of Belarus are at the final stage of development. In this connection, in order to expand the resource base, Belarusian oil companies are assigned with the task of searching, exploring and developing hard-to-recover reserves. In recent years, a number of geological works have been carried out to search and study the sedimentary cover rocks of the Belarusian part of the Pripyat Trough, the results of these works were the discovery of promising deposits of the Petrikov Horizon of the Upper Devonian. These deposits are represented by dense fractured carbonate rocks with ultra-low permeability (less than 0.01 mD) and low effective porosity (up to 10%). The most promising technology for the development of such reservoirs is the drilling of horizontal wells and the subsequent implementation of Multistage hydraulic fracturing. This article presents the experience of developing ultra-low-permeability reservoirs in the Republic of Belarus in the period 2014-2021, briefly describes the main technologies used, the evolution of technological solutions for effective involvement in the active development of hard-to-recover reserves.

Advancement of Hydraulic Fracture Diagnostics in Unconventional Formations

Multistage hydraulic fracturing is a technique to extract hydrocarbon from tight and unconventional reservoirs. Although big advancements occurred in this field, understanding of the created fractures location, size, complexity, and proppant distribution is in its infancy. This study provides the recent advances in the methods and techniques used to diagnose hydraulic fractures in unconventional formations. These techniques include tracer flowback analysis, fiber optics such as distributed temperature sensing (DTS) and distributed acoustic sensing (DAS), tiltmeters, microseismic monitoring, and diagnostic fracture injection tests (DFIT). These techniques are used to estimate the fracture length, height, width, complexity, azimuth, cluster efficiency, fracture spacing between laterals, and proppant distribution. Each technique has its advantages and limitations, while integrating more than one technique in fracture diagnostics might result in synergies, leading to a more informative fracture description. DFIT analysis is critical and subjected to the interpreter’s understanding of the process and the formation properties. Hence, the applications of machine learning in fracture diagnostics and DFIT analysis were discussed. The current study presents an extensive review and comparison between different multistage fracture diagnostic methods, and their applicability is provided. The advantages and the limitations of each technique were highlighted, and the possible areas of future research were suggested.

Increasing the Productivity of Horizontal Wells Through Multistage Hydraulic Fracturing Using a Working Fluid Based on a New Biopolymer System

According to the US Energy Agency (EIA), Russia is the world leader in terms of the volume of technically recoverable "tight oil" resources (U.S. Department of Energy, 2013). To convert them into commercial production, it is necessary to create cost-effective development technologies. For this purpose, a strategy has been adopted, which is implemented at the state level and one of the key elements of which is the development of the high-tech service market. In 2017, the Minister of Energy of the Russian Federation, in accordance with a government executive order (Government Executive Order of the Russian Federation, 2014), awarded the Gazprom Neft project on the creation of a complex of domestic technologies and high-tech equipment for developing the Bazhenov formation with the national status. It is implemented in several directions and covers a wide range of technologies required for the horizontal wells drilling and stimulating flows from them using multi-stage hydraulic fracturing (MS HF) methods. Within the framework of the technological experiment implemented at the Palyanovskaya area at the Krasnoleninskoye field by the Industrial Integration Center "Gazpromneft - Technological Partnerships" (a subsidiary of Gazprom Neft), from 2015 to 2020, 29 high-tech wells with different lengths of horizontal wellbore were constructed, and multistage hydraulic fracturing operations were performed with various designs. Upon results of 2020, it became possible to increase annual oil production from the Bazhenov formation by 78 % in comparison with up to 100,000 tons in 2019. The advancing of development technologies allowed the enterprise to decrease for more than twice the cost of the Bazhenov oil production from 30 thousand rubles per ton (69$/bbl) at the start of the project in 2015 to 13 thousand rubles (24$/bbl) in 2020. A significant contribution to the increase in production in 2020 was made by horizontal wells, where MS HF operations were carried out using an experimental process fluid, which is based on the modified Si Bioxan biopolymer. This article is devoted to the background of this experiment and the analysis of its results.

Experience in Optimizing the Location and Parameters of Multistage Hydraulic Fractures for a Multilateral Well Based on Reservoir Simulation

This work presents the approaches used for the optimal placement and determination of parameters of hydraulic fractures in horizontal and multilateral wells in a low-permeability reservoir using various methods, including 3D modeling. The results of the production rate of a multilateral dualwellbore well are analyzed after the actual hydraulic fracturing performed on the basis of calculations. The advantages and disadvantages of modeling methods are evaluated, recommendations are given to improve the reliability of calculations for models with hydraulic fracturing (HF)/ multistage hydraulic fracturing (MHF).