Tight oil reservoir production characteristics developed by CO2 huff ‘n’ puff under well pattern conditions

Tight oil reservoirs have poor physical properties, and the problems including rapid oil rate decline and low oil recovery degree are quite common after volume fracturing. To obtain a general understanding of tight oil reservoir production improvement by CO2 huff ‘n’ puff, the high-pressure physical properties of typical tight oil samples are measured. Combining the typical reservoir parameters, the production characteristics of the tight oil reservoir developed by the CO2 huff ‘n’ puff are numerically studied on the basis of highly fitted experimental results. The results show that: (1) during the natural depletion stage, the oil production rate decreases rapidly and the oil recovery degree is low because of the decrease in oil displacement energy and the increase in fluid seepage resistance. (2) CO2 huff ‘n’ puff can improve the development effect of tight oil reservoirs by supplementing reservoir energy and improving oil mobility, but the development effect gradually worsens with increasing cycle number. (3) The earlier the CO2 injection timing is, the better the development effect of the tight reservoir is, but the less sufficient natural energy utilization is. When carrying out CO2 stimulation, full use should be made of the natural energy, and the appropriate injection timing should be determined by comprehensively considering the formation-saturation pressure difference and oil production rate. The research results are helpful for strengthening the understanding of the production characteristics of tight oil reservoirs developed by CO2 huff ‘n’ puff.

Development Characteristics and Finite Element Simulation of Fractures in Tight Oil Sandstone Reservoirs of Yanchang Formation in Western Ordos Basin

Structural fractures have a significant control effect on the large-scale accumulation of hydrocarbons in the Yanchang Formation. Previous studies have affirmed the important role of fractures in hydrocarbon accumulations in strongly deformed zones. However, for low-amplitude structural areas, the degree of fracture development is relatively low, and their control on sweet spots of hydrocarbons has not yet formed a unified understanding. In this paper, taking the Upper Triassic Yanchang Formation in the western Ordos Basin as an example, the development characteristics, prediction method, and the distribution of fractures in tight sandstone reservoirs in low-amplitude structural areas have been systematically studied using a large number of cores, thin sections, paleomagnetism, FMI logging, acoustic emission, productivity data, and finite element method. The research results showed that the Yanchang Formation in the study area mainly develop high-angle and vertical fractures, which were formed by regional tectonic shearing. Fractures are mainly developed in the fine-grained and ultra-fine-grained sandstones of the distributary channel and estuary bar microfacies, while the fractures in the medium-grained sandstones of the distributary channel and the mudstones of the distributary bay are relatively underdeveloped. The core fractures and micro-fractures of the Yanchang Formation all have the regional distribution characteristics, and the fracture strikes are mainly between NE50° and NE 70°. Moreover, the finite element method was used to predict the fractures in the target layer, and the prediction results are consistent with the actual distribution results of the fractures. The coupling analysis of fractures and tight oil sandstone distribution showed that the existence of fractures provided conditions for the accumulation of hydrocarbons in the Yanchang Formation. The confluence and turning areas of the river channels were repeatedly scoured by river water, and the rocks were brittle and easy to form fractures. The thickness of the fractured sandstone in these areas is usually greater than 0.4 m. Moderately developed fracture zones are prone to form hydrocarbon accumulation “sweet spots,” and the fracture indexes of these areas are usually distributed between 0.8 and 1.2. However, when the fracture index exceeds 1.2, over-developed fractures are unfavorable for the accumulation of hydrocarbons.

Forecast of Economic Tight Oil and Gas Production in Permian Basin

We adopt a physics-guided, data-driven method to predict the most likely future production from the largest tight oil and gas deposits in North America, the Permian Basin. We first divide the existing 53,708 horizontal hydrofractured wells into 36 spatiotemporal well cohorts based on different reservoir qualities and completion date intervals. For each cohort, we fit the Generalized Extreme Value (GEV) statistics to the annual production and calculate the means to construct historical well prototypes. Using the physical scaling method, we extrapolate these well prototypes for several more decades. Our hybrid, physico-statistical prototypes are robust enough to history-match the entire production of the Permian mudstone formations. Next, we calculate the infill potential of each sub-region of the Permian and schedule the likely future drilling programs. To evaluate the profitability of each infill scenario, we conduct a robust economic analysis. We estimate that the Permian tight reservoirs contain 54–62 billion bbl of oil and 246–285 trillion scf of natural gas. With time, Permian is poised to be not only the most important tight oil producer in the U.S., but also the most important tight gas producer, surpassing the giant Marcellus shale play.

An ESP Production Optimization Algorithm Applied to Unconventional Wells

The objectives and Scope is to evaluate the feasibility of a Production Maximization algorithm for ESPs on unconventional wells using projected operating conditions instead of current ones, which authors expect will be crucial in adjusting the well deliverability to optimum frequencies on the rapidly changing conditions of tight oil wells. Actual production data for an unconventional well was used, covering from the start of Natural Flow production up to 120 days afterwards. Simulating what the production would be if a VFD running on IMP Optimization algorithms had been installed, new values for well flowing pressures were calculated, daily production scenarios were evaluated, and recommended operating frequencies were plotted. Result, observations, and conclusions: A. Using the Intelligent Maximum Production (IMP) algorithm allows maximum production from tight oil wells during the initial high production stage, and the prevention of gas-locking at later stages when gas production increases. B. The adjustment of frequency at later stages for GOR wells is key to maintaining maximum production while controlling free gas at the intake when compared against controlling the surface choke. Novel/additive information: The use of Electrical Submersible Pumps for the production of unconventional wells paired with the use of a VFD and properly designed control algorithms allows faster recovery of investment by pumping maximum allowable daily rates while constraining detrimental conditions such as free gas at the intake.

How Do Bankruptcies in the Shale Sector Induce Operators to Focus on Value Creation?

Between January 2015 and early 2021, about 76 of the approximately 2,160 small-to-medium independent companies in the tight oil sector filed for Chapter 11 protection. These filings mostly occurred in 2016 and 2019. These companies were negatively impacted by the low oil prices in these years owing to their lack of financial discipline and poor financial risk assessments. As a result, they declared bankruptcy. News outlets tend to amplify bankruptcy filing announcements in the oil and gas sector. Nevertheless, our analysis shows that these bankruptcy declarations do not imply that the shale oil and gas sector collapsed. The ailing operators in 2019 were responsible for about 8.5% of total tight oil production in the United States. This volume did not disappear from the market because of the Chapter 11 provisions. Instead, the ailing operators either became more efficient and financially disciplined or transferred their assets to more efficient operators. Over 33 independent companies have ultimately emerged from bankruptcy. These companies successfully reached debt restructuring resolutions with their investors, transferred equity ownership to investors or sold or leased their assets to other operators. Companies that failed to adapt exited the oil market through either liquidation or acquisitions by other companies. Going forward, more consolidations are expected in the shale industry, especially among medium-to-large independent producers that accrued large debts in previous years. These producers will either enter bankruptcy owing to financial headwinds and market uncertainty or be acquired by larger companies. This analysis shows that bankruptcies in the tight oil sector may be viewed positively or negatively depending on the situation and perspective. Bankruptcies do incur different types of costs and losses to many parties. However, consolidation that improves the efficiency of resource allocation can be viewed as a positive sign for the economy. Operators, equity owners, debtors-in-possession and the oil and gas industry can therefore view bankruptcies within the industry differently.

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