Shale gas well productivity potential evaluation based on data-driven methods: case study in the WY block

Evaluating the productivity potential of shale gas well before fracturing reformation is imperative due to the complex fracturing mechanism and high operation investment. However, conventional single-factor analysis method has been unable to meet the demand of productivity potential evaluation due to the numerous and intricate influencing factors. In this paper, a data-driven-based approach is proposed based on the data of 282 shale gas wells in WY block. LightGBM is used to conduct feature ranking, K-means is utilized to classify wells and evaluate gas productivity according to geological features and fracturing operating parameters, and production optimization is realized through random forest. The experimental results show that shale gas productivity potential is basically determined by geological condition for the total influence weights of geologic properties take the proportion of 0.64 and that of engineering attributes is 0.36. The difference between each category of well is more obvious when the cluster number of well is four. Meanwhile, those low production wells with good geological conditions but unreasonable fracturing schemes have the greatest optimization space. The model constructed in this paper can classify shale gas wells according to their productivity differences, help providing suggestions for engineers on productivity evaluation and the design of fracturing operating parameters of shale gas well.

The First Behind-Casing Fiber-Optic Installation in a High-Pressure High-Temperature Deep Gas Well in Oman

This paper discusses the first fiber-optic (FO) installation in a vertical high-pressure high-temperature deep gas well in PDO, Oman. A specially designed fiber-optic cable was successfully installed and cemented behind the production casing, which was subsequently perforated in an oriented manner without damaging the cable. This paper also describes how the fiber-optic cable was used afterwards to acquire Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) data for the purpose of hydraulic fracturing diagnostics. Fiber-optic surveillance is becoming an increasingly important activity for well and reservoir surveillance. The added complexity of the fiber-optic installation will affect the well design, which is one of the elements that requires focused attention, especially when the fiber is installed behind casing. The impact on casing design, wellhead design, perforation strategy, and logging requirements will all be discussed. In order for a well to be completed with a permanent fiber-optic cable, a few critical procedures need to be followed, including: –modifying the wellhead design to include feedthrough ports for the cable;–optimizing the cement design;–imposing strict procedures to ensure the cable is installed behind the casing without getting stuck;–changing the perforation phasing to avoid damaging the cable;–mapping the location of the cable to allow the gun string to be oriented away from the cable. The fiber-optic cable itself needed to be designed to be protected in such a way that it would not be damaged during installation and completion (perf/frac) activities. Furthermore, the cable was also optimized to improve its detectability, to aid the oriented perforation. In deep gas wells, much more than in conventional shallow water injectors or oil producers, the well integrity aspect should be given special attention. Specifically, any risks related to unwanted gas leaks, either through the control line, poor cement, or because of other design errors should be avoided. In deep gas wells, high temperature and pressure will also play a big role in the expected lifespan of the cable. Finally, the well was hydraulically fractured in four stages, using the "plug-and-perf" technique, during which DAS and DTS data were acquired continuously and across all depths of the well. The data provided valuable information on the effectiveness of each of the frac stages, it could be used to analyze screen-outs and detect out-of-zone injection, and recommendations for the optimizations of future hydraulic frac designs could be derived. The fiber-optic data were also integrated with other open-hole data for improved understanding of the reservoir performance. The next step will be to acquire repeated time-lapse DAS and DTS data for production profiling, to gain more insights of how the long-term production performance is affected by the hydraulic frac operations.

Development of well complexity calculator and its integration into standard well engineering management system/well delivery system

Oil and gas well drilling is the most important and complex task for oil and gas exploration. It is not necessary that design and execution complexity remain the same for two different wells even in the same field. It is possible to have a very complex well to drill after a very straightforward simple well being drilled earlier in the same field. Making correlation or comparison of any of the two or more than two oil and gas drilling wells is an ongoing debate in the petroleum industry. Generally, companies compare the oil and gas drilling wells on a single or two parameters, for example: time versus depth, directional trajectories, well cost and/or other single factors in disengagement of one another. In order to compare two different types of oil and gas drilling wells, having distinctive design, drilling and fluid program and challenges, a scientific rating system is required, which can relate various wells with one another. In this research paper, a calculator named Well Complexity Calculator has been developed to measure the complexity of the oil and gas well drilling by using different parameters. All these parameters are commonly affecting the drilling program and its execution. Secondly, a methodology is designed for integration of Well Complexity Calculator into standard Well Engineering Management System/Well Delivery System for better execution of drilling program. Fifty-one (51) oil and gas drilling well complexity parameters have been utilized to develop Well Complexity Calculator, where they are categorized into three main complexities types named Design Well Complexity, Geological Well Complexity and Project Well Complexity. Design and Geological Well Complexities combine to form Drilling Well Complexity, and then Drilling Well Complexity and Project Well Complexity combine to form Well Complexity. Median, Mode and Monte Carlo simulation techniques were chosen to develop the calculator where Median showed best suited results and was accordingly chosen for the final calculator. Sixty-six (66) actual oil and gas wells’ camouflaged drilling data were used to analyze and fine tune the developed Well Complexity Calculator. Output complexities of these wells were falling in different complexity levels. Moreover, it was seen that the number of low, high and medium complexity wells was different for Design, Geological, Project, Drilling and Well Complexities which is in line with the real-world scenario.The findings and the output Well Complexity Calculator can be very useful at any stage from initial planning to close-out of a well. Without the application of a system like Well Complexity Calculator, wells are categorized as low, medium or high complexity based on either two to three major parameters or based on qualitative assessment of team involved in the project. Here, step-by-step procedure is developed and explained by which any company involved in Drilling and Well Operations can develop their own Well Complexity Calculator and then accordingly integrate it into their Well Engineering Management System/Well Delivery System.

Choosing a methodological base for forming and accounting for the construction costs of a gas well at the final stage of field development

The article introduces the problems of choosing a methodological base for forming and accounting costs during well construction, taking into account the intensification of gas inflow at the final stage of field development. The main methods that allow taking into account the costs of drilling operations are outlined. The main costs that need to be taken into account when designing fields with hard-to-recover gas reserves are identified and characterized. The main stages of cost formation by construction phases of a gas-producing well are shown, as well as the factors influencing the level and structure of the cost price during the construction of a well are highlighted. The authors consider the classification of cost accounting methods in the context of the comparison criterion and present the possible results of the correct choice of the cost formation method during the construction of a gas well at the final stage of its development.

The expansion of innovative activity on rise of oil production enterprises in Azerbaijan

The article analysis the oil and gas production condition in the Republic on basis of statistical data of many years as well as the level of investment provision. The article estimates the structure of expenses on innovative techniques, the condition of exploitation of oil and gas boreholes, the implementation of geological and technological actions, the ways of exploitation methods as well as the methods of ledge effects and influence on extra oil production. It also shows up the reserves and ways of their rational usage. Keywords: innovative activity; geological and technological actions; oil and gas; well.

The method for study of vertical gas-liquid flow with foaming agent

The issue of operation water-cut and "self-kills" wells is one of major aspects in gas production. One of the methods of solving this problem is the introduction of foaming agent into the well. The effectiveness of these technologies requires a theoretical and experimental study of gas-liquid flow with surfactants. We have analyzed existing works and have found out that experimental research in this area was carried out at atmospheric pressure. At the same time, the pressure in the well varies with the length of the wellbore and can affect the properties of foaming agent. The article presents a description of a facility for the study of gas-liquid flows with foaming agents at different pressure values. A method of conducting experiments on the facility, simulating a section of the production tubing of a vertical gas well, has been developed. The relations allowing calculating the volume contents of the phases in the gas-liquid flow with surfactants are proposed.

Features of gas inflow to a horizontal wellbore at various trajectories

This article discusses the effect of wellbore trajectory on the flow performance of a horizontal cased and perforated gas well. We used a coupled well-reservoir flow model, taking into account the nature of the flow, and local hydraulic resistances of the wellbore, and thus determined the pressure and mass flow distribution along the horizontal wellbore for several types of trajectories, including undulated and toe-up trajectories. The simulation results showed the effect of horizontal gas well trajectory type on its flow rate and the importance of considering pressure distribution to optimize well design.

On the One-Point Model for the Productivity Evaluation in Jingbian Sector of Yan’an Gas Field

The productivity equation of a gas well is, in the final analysis, an expression that describes the relationship between the production of a gas well and its bottom-hole flowing pressure. There are two kinds of productivity equations in common use at present: binomial productivity equation and exponential productivity equation. Combined with the modified isochronal well test, the test data are interpreted, and it is found that the open flow rates calculated by the two productivity equations are basically the same when the pressure difference at the test point is large, and the deviation of the exponential productivity equation is large when the pressure difference at the test point is small. Using binomial productivity equation and modifying isochronous well test, we established the single-point deliverability formula for the Jingbian sector of the Yan’an gas field. The field experience formula and production data are used to verify it. Their average errors are 2.59% and 7.12%, respectively; and the coincidence rate of productivity evaluation is 90%. The one-point productivity formula established has high precision and is suitable for productivity analysis of gas wells in paleozoic reservoirs in the Jingbian sector of the Yan’an gas field. This paper provides insights into the one-point productivity evaluation and its future application in the gas field.

NanoGram Detection of Drilling Fluids Additives for Uncertainty Reduction in Surface Logging

Manual sampling rock cuttings off the shale shaker for lithology and petrophysical characterization is frequently performed during mud logging. Knowing the depth origin where the cuttings were generated is very important for correlating the cuttings to the petrophysical characterization of the formation. It is a challenge to accurately determine the depth origin of the cuttings, especially in horizontal sections and in coiled tubing drilling, where conventional logging while drilling is not accessible. Additionally, even in less challenging drilling conditions, many factors can contribute to an inaccurate assessment of the depth origin of the cuttings. Inaccuracies can be caused by variation of the annulus dimension used to determine the lag time (and thus the depth of the cuttings), by the shifting or scrambling of cuttings during their return trip back to the surface, and by the mislabelling of the cuttings during sampling. In this work, we report the synthesis and application of polystyrenic nanoparticles (NanoTags) in labeling cuttings for depth origin assessment. We have successfully tagged cuttings using two NanoTags during a drilling field test in a carbonate gas well and demonstrated nanogram detection capability of the tags via pyrolysis-GCMS using an internally developed workflow. The cuttings depth determined using our tags correlates well with the depth calculated by conventional mud logging techniques.