28 February 2025, Volume 19 Issue 1

    

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GEOLOGY AND EXPLORATION
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  Evaluating geology-engineering sweetspots in carbonate reservoirs, DK13 well area, Daniudi gasfield

  JIANG Yanfang

  Natural Gas Technology and Economy. 2025, 19(1): 1-5. https://doi.org/10.3969/j.issn.2095-1132.2025.01.001

  Abstract ( ) Download PDF (3264KB) ( ) Knowledge map Save

  In Daniudi gasfield, Ordos Basin, production differs greatly in porous carbonate reservoirs even after hydraulic sand fracturing due to strong reservoir heterogeneity. Thus, a model was established to compute the production contribution of each layer, and a heat map matrix chart was created on both geology-engineering parameters and production data. Moreover, the major geology-engineering factors influencing on the production were analyzed to evolve into a formula for evaluating double sweetspots and calculating productivity. Results show that (i) the production contribution in fifth submember of Majiagou 5 Member (Ma 5⁵, hereinafter same) negatively correlates with gamma ray and positively with interval transit time, bulk density and gas saturation. While that of Ma 5⁶⁺⁷ is positively correlated with reservoir thickness, bulk density and neutron porosity; (ii) the production in Ma 5^5-7 is in high correlation with reservoir thickness, maximum total hydrocarbon, porosity, gas saturation, and injected fracturing-liquid, and acid proppant volume; (iii) the established double-sweetspot index calculation model for Ma 5^5-7 is dependent on multiple factors, and the calculated index has the correlation of 0.937 5 with the production; and (iv) the created production prediction model is on the basis of the double-sweetspot index, and the error between the predicted and actual production is less than 2%. In conclusion, with high coincidence with reality, both geology-engineering sweetspot and productivity prediction models which provide active guidance for selecting staged fracturing and designing optimal fracturing are worth popularizing.
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  Gas logging interpretation chart and its application to Shunbei field

  YANG Xudong

  Natural Gas Technology and Economy. 2025, 19(1): 6-12. https://doi.org/10.3969/j.issn.2095-1132.2025.01.002

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  There are two problems appeared in four gas logging charts (triangle, 3H, specific value, and logarithmic charts) which are currently used in Shunbei field, for example inconsistent conclusions interpreted on oil and gas show, and great difference among completing test results. Thus, taken 157 wells in this field as examples, some data on mud-logging display and completing test information in some of the wells were gathered together and then selected to analyze the diversity in the occurrence of natural gas in reservoirs, the difference in the dissolution and precipitation of various component in water and crude oil, and the gas chromatography principle of composite logging instrument. In addition, two identifying parameters of humidity and oil-water separation coefficient were determined, and a crossplot chart was also developed. Better endings have been achieved in the trial of 28 wells newly drilled in this field. Results show that (i) the proportion of each component in total hydrocarbon can be calculated according to its molar mass even though total hydrocarbon and component are attached to different analysis systems; and (ii) the humidity can effectively separate a gas layer from oil or water layers in the chart, while the separation coefficient can obviously separate a water layer from an oil layer in the chart. In conclusion, the difference between total hydrocarbon and the sum of each component can qualitatively reflect the content of heavy component in the fluid. What's more, the chart with the humidity as the vertical axis and the separation coefficient as the horizontal axis can better discriminate fluid properties in Shunbei field.
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  Production dedication of each interval in horizontal wells of tight carbonate reservoirs and its main controls: An example from Daniudi gasfield, Ordos Basin

  WU Yue

  Natural Gas Technology and Economy. 2025, 19(1): 13-19. https://doi.org/10.3969/j.issn.2095-1132.2025.01.003

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  At present, the Lower Paleozoic carbonate gas reservoirs are regarded as the main productivity substitute in Daniudi gasfield. But how each interval dedicates to the production in carbonate horizontal wells is unclear, and the main controls on this dedication are ambiguous as well, all conditioning the production increase, cost reduction and efficiency improvement. To this end, some difference among these intervals was found out through liquid-producing profile tested by coiled tubing. In addition, the main controls was made clear. Results show that (i) the stimulation size exerts little impact on each interval production when one horizontal interval is located in certain reservoirs with better physical properties, and these properties and gas content as fundamental factors can affect the productivity in each interval; and (ii) when one interval is located in other reservoirs whose physical properties are poor with small difference, the physical properties, gas content and fracturing scale still have little impact on each interval production. Nevertheless, stimulation may be gained in such poor reservoirs through special fracturing. In conclusion, it is recommended for carbonate gas reservoirs in horizontal wells to prioritize the deployment in favorable blocks developed with fractured-porous reservoirs, followed by appropriately increasing the stimulation scale for efficiency improvement in tight carbonate gas reservoirs. What's more, for a certain block developed with porous reservoirs, it is supposed to make differentiated stimulation measures for various reservoir types to achieve effective production in each interval.
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  A method for calculating formation pressure in sour gas reservoirs, T block, northeastern Sichuan Basin

  FENG Ziyi, WU Hongli, YOU Junyu, REN Hongming, JIANG Xingxin, HE Zi'ang, HUANG Xiaoliang

  Natural Gas Technology and Economy. 2025, 19(1): 20-26. https://doi.org/10.3969/j.issn.2095-1132.2025.01.004

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  A lack of data on initial pressure in sour gas reservoirs, T block, northeastern Sichuan Basin, may bring about much hardship in sorting out change laws of formation pressure during reservoir development. Thus, a model was built to predict the sulfur solubility in such reservoirs according to dynamical data. Then, gas composition and some critical parameters were computed by means of gas chromatography experiments, and one approach to correct a deviation factor was selected to analyze the material-balance equation with consideration of sulfur deposition in these reservoirs. Finally, a formation-pressure calculation method which combines the equation with the correction was proposed. Results show that (i) the minimum relative error from DPR and Gopal approaches to measure the deviation factor is respectively 0.39% and 2.85% on average, indicating that these two approaches are more suitable for sour gas reservoirs in northeastern basin; (ii) the average error between calculations from the proposed method and the measured formation pressure ranges from 1.93% to 3.15%, standing for this newly method with smaller error than that from traditional ones, is more accuracy; and (iii) since there is no need for this method to hold that much data, it can reduce loss caused by shut-in pressure measurement in sour gas reservoirs with high yield.
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  Predicting geological sweetspots in Ma 5¹⁺² submember of weathered crust reservoirs, Daniudi gasield, Ordos Basin

  LIU Jia

  Natural Gas Technology and Economy. 2025, 19(1): 27-36. https://doi.org/10.3969/j.issn.2095-1132.2025.01.005

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  The fifth member of the Ordovician Majiagou Formation (Ma 5 Member) in Daniudi gasfield is standing in regression. Vertically, it is divided into 10 submembers (Ma 5¹ to Ma 5¹⁰), among which Ma 5¹⁺² is still in relative regression. Numerous dissolved pores, vugs and fractures induced from fresh water leaching and karstification are extended into Ma 5¹⁺² where gray dolomite is dominantly developed with a little limestone to accumulate hydrocarbon. Therefore, cores, well- and mud-logging data from over 580 wells drilling through the target were analyzed to predict geological sweetspots of Ma 5¹⁺² in this field. And that there developed 4 types of sedimentary microfacies, including calcareous dolomite flat, dolomite flat, dolomitic limestone flat, and argillaceous dolomite flat, was pointed out. Furthermore, combined with paleogeomorphological natures, the thickness distribution of Ma 5¹⁺² reservoirs on the plane was characterized. By referring to production data of gas wells, the extension of quality reservoirs was predicted, and the sweetspots were delineated. Results show that (i) 7 episodes of sedimentary cycle are developed vertically in Ma 5¹⁺² where shale content increases from below, meaning the decreasing trend of waterbody depth and salinity while this content decreases from north to south on profile, implying the increasing trend of waterbody depth and salinity; and (ii) Ma 5¹⁺² reservoirs overall get thicker to the west, and their thickness varies greatly along north to south, with the maximum thickness difference of 24 m, but gently along east to west, with the maximum difference of 8 m. Six geomorphological units are identified, i.e., karst platform mound, monadnock, slope, highland, low-lying land and trough, and the reservoirs are mainly located in the first two units. In conclusion, the quality reservoirs are mainly deposited in both calcareous dolomite flat and dolomite flat. Rich in dolomite extended from northeast to southwest, the residual reservoirs are thick. This thickness often exceeds 4 m in both platform mound and monadnock, and that from 2 to 6 m in slope. Additionally, three sweetspot zones are selected on the basis of predominant microfacies, lithofacies and paleogeomorphological units. With the porosity exceeding 2.5%, the quality reservoirs are over 4 m in thickness. Imaging logging presents that fractures, dissolved pores and vugs are well developed, indicating better physical properties. Both gas saturation and total hydrocarbon content are over 15% and 20%, respectively. The testified cumulative production is more than 2000×10⁴ m³.
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  Appraisal of the effect of geophysical prospecting projects during their full lifecycle,ST block, Tarim Basin

  HAN Zhao, TAN Yuping, ZHOU Gang, RAN Qi, LI Chunlei, LIAO Zhifang, MA Zhiquan, LUO Yang

  Natural Gas Technology and Economy. 2025, 19(1): 37-44. https://doi.org/10.3969/j.issn.2095-1132.2025.01.006

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  Taken fourteen geophysical prospecting projects in ST block as examples, three appraisal indexes including technical, application and economic effect were discussed for these projects during their full lifecycle in an effort to create the post evaluation system of prospecting effect, optimize exploration and development strategies, select the project access to investment, increase technical process and expand application profits. In addition, both route plan and computing workflow were proposed for the appraisal index system with five levels in the transverse direction. Results show that (i) among these fourteen projects, three ones like SN41N are regarded as the type I project due to excellent effect, nine ones such as AD with moderate effect as the type II, and the rest two projects with poor effect as the type III; and (ii) the re-inspection also demonstrates the appraisal results in line with practice in the study area. In conclusion, it is essential to continuously upgrade technological level in acquisition and interpretation of seismic data, to deepen the research on geological conditions to form reservoirs, to improve reservoir-protection skills, and to speed up the popularization of prospecting achievements. Figuring out the similarity and difference and their origin, our methodology may support technical advancement and is conducive to enhancing both management efficiency and exploration benefits for the projects. With quantifiable and attainable natures and strong practicality, the scientific and rational methodology gives expression to output efficiency and contributory value in projects' total process.
DEVELOPMENT ENGINEERING
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  A remote control system for logging technologies and its application to Shengli oilfield

  YANG Ping, YI Jun, HAN Shangke, HOU Junqing, WEI Linna, LI Ning, HU Xiaopei

  Natural Gas Technology and Economy. 2025, 19(1): 45-49. https://doi.org/10.3969/j.issn.2095-1132.2025.01.007

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  Smart logging technologies have been increasingly applied to petroleum companies with the digital and intelligent advancement. Especially remote skills emerge as the times require to resolve difficulties in conventional logging, such as long well occupation time, big logging costs, low efficiency and high labor intensity. Remote control of logging equipment can be attained by means of wireless transmission, so that experts as well as technical and safety personnel can examine and analyze data, and regulate parameters to guarantee all logging operation in high quality, efficiency and safety. Results show that (i) the established new remote control system is well applicable to logging operation; (ii) its application acquires real-time monitoring and transferring logging curves from numerous wells, solves on-site abnormalities in time, reduces well occupation time and logging costs, and optimizes human resources; and (iii) promoting this system is of guiding significance for next breakthrough made in core online logging technologies, and collaborative innovation across well areas and departments.
DOUBLE CARBON AND NEW ENERGY
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  Temporal-spatial characteristics and influential factors of carbon emission from energy consumption in Sichuan-Chongqing area

  LI Qiaochu, CHEN Junhua, ZHANG Peng

  Natural Gas Technology and Economy. 2025, 19(1): 50-60. https://doi.org/10.3969/j.issn.2095-1132.2025.01.008

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  Holding the decisive essence leading to some regional variations in the carbon emission from energy consumption and taking relevant emission-reduction measures are the prerequisites for achieving the dual-carbon goal. Therefore, taken Sichuan-Chongqing area as an example, a carbon-emission inventory which regarded both fossil-fuel combustion and power allocation in different areas was constructed, and the effect of multiple influential factors was discussed on the basis of the Kaya Identity and LMDI model in order to figure out both temporal-spatial characteristics and influential factors of this emission. Results show that (i) a decreasing trend emerged in the carbon emission from energy consumption in Sichuan Province from 2015 to 2022 while an increasing trend in Chongqing City due to the endowment diversity among renewable energy resources. The emission from energy processing and conversion is rooted in thermal power generation and heating sectors. In terms of terminal expenditure, the largest emission source comes from industrial field, followed by transportation and residential life, then business and other services, and both agriculture and building industry making a small contribution to the emission. Sichuan advances the low-carbon strategy in addition to ensuring the energy's supply-demand security through transporting large amount of water and electricity resources, while Chongqing indirectly raises its carbon contribution via relying on external power output; and (ii) as an inhibiting factor, the structure of energy use makes the incremental contribution to the Sichuan's emission year by year while little impact in Chongqing. For the energy intensity as a key factor for emission reduction, its inhibition peaked in 2016-2017 due to benefits from the dual control in the energy use. The industrial structure in Sichuan is an inhibition factor as well, and its influence is slowly diminishing, while that in Chongqing increases first and then decreases with changes of secondary industries' proportion. The economic growth whose effect is on the decease each year under the new pattern of low carbon is also a critical factor in emission acceleration. The effect of population development is affected by population size, social culture, and resource allocation comprehensively.
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  Development potential of carbon asset from natural-gas residual pressure power generation and methodological design

  WANG Hanyue, LI Sensheng, ZHANG Shun, HAN Cuilian, LI Yingfei, CHEN Can

  Natural Gas Technology and Economy. 2025, 19(1): 61-68. https://doi.org/10.3969/j.issn.2095-1132.2025.01.009

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  Some investigation and professional discussion have been carried out in an effort to estimate the development potential of carbon asset from natural-gas residual pressure power generation and make this generation's methodology meeting filing requirements of the Ministry of Ecology and Environment of the People's Republic of China. Furthermore, the key to work out this methodology was analyzed according to methodological compilation needs through reference on a carbon-credit system of CDM. In addition, the decisive elements were proposed for the compilation of such generation methodology, and an additional and monitoring management was designed. Results show that (i) via the evaluation on the potential of both residual pressure power generation and carbon-asset development in different links such as oil and gasfields, long-distance pipelines, and gate stations, these two sorts of potential achieved are 145.73×10⁸ kWh/a and 811.44×10⁴ tCO₂e/a, respectively; (ii) as for the additional methodological design, baseline scenarios are made certain to contrast the additionality. And it is proposed to directly adopt exemption from demonstration based on the potential analysis on power generation and practical work; and (iii) as for the monitoring design of methodology, the principles of credibility, accuracy and conservation should be followed, and monitoring projects' boundaries are described. Parameters and data which should be relatively surveyed in not only design but implementation stages, and the method to ensure surveying quality is defined by using emission-reduction calculations.
OPERATION AND MANAGEMENT
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  Constructing an index system to evaluate the development ability in petroleum companies

  YU Zhibo, LU Yanlin, ZHOU Juan, GU Chaohui, WU Mengxi, GUO Lu

  Natural Gas Technology and Economy. 2025, 19(1): 69-75. https://doi.org/10.3969/j.issn.2095-1132.2025.01.010

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  It's essential for state-owned enterprises to highlight the collaborative and mutual enhancement of hard and soft power in 2025 when is the last year of the 14th Five-Year Plan so as to scale up their ability to concentrate or expand core functions, improve core competitiveness, and promote high-quality development. Petroleum companies which are an integral part to these enterprises are badly in need of constructing a quantified index system for evaluating the development ability related to each link of industrial chain. Thus, the evaluation system has been constructed through some theoretical analysis on the companies' development ability according to three principles of system science, business dominant, and continuous improvement. Results show that (i) petroleum companies are classified into four major business segments in accordance with their business natures and functional positioning, and a general evaluation index system framework is also established for each segment; (ii) 26 indexes, 20 indexes, 20 indexes and 23 indexes individually from production, market competition, security and scientific research segments are selected to constitute an all-round index system in accordance with the major in general indexes with the minor in individual ones; and (iii) both definition and calculating instruction are ascertained for the main indexes. In conclusion, this quantified evaluation system which is related to each link of industrial chain can fully judge petroleum companies, objectively estimate their value dedication, identify operation and management problems, and promote the transformation towards refined and lean supervision.
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  Helium resources in the USA: Industrial development, exploration and enlightenment

  WANG Haihua

  Natural Gas Technology and Economy. 2025, 19(1): 76-82. https://doi.org/10.3969/j.issn.2095-1132.2025.01.011

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  Helium has been widely used in numerous fields such as commerce, industry, healthcare, national defense, and scientific research. However, it is in short supply in China and its external dependence rate attains as high as 90%. Most of helium is primarily imported from the USA, Qatar and Australia, leading to severe resource safety. Thus, taken the USA which is the world's largest helium producer, consumer and exporter as an objective to analyze the development history of its helium industry, the government's policies on helium and natural gas, and the helium resource exploration through reviewing lots of domestic and foreign literature. Results show that (i) the American helium industry has a long development history, and the policies related to helium gas have a profound impact on both industrial development and exploration progress. And American experience may provide reference for other countries; and (ii) helium is becoming one of the main exploration targets in the USA in spite of a by-product of conventional gas in its initial exploration. In conclusion, China should make rules to ascertain helium's strategic role and strengthen its industrial governance, to strategize helium reserves and build the reserves to balance supply and demand, to find out helium accumulation laws and explore additional exploration targets in different geological setting, to strengthen international cooperation with a greater range of countries rich in helium resources, especially those along the "the Belt and Road", and to carry out cooperation projects to solve the problem of helium resource supply and improve helium security insurance.
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  "1+N" management mode of clean production for tight gas, Tianfu gasfield

  WANG Yixi, DANG Lurui, BAO Manzhu

  Natural Gas Technology and Economy. 2025, 19(1): 83-88. https://doi.org/10.3969/j.issn.2095-1132.2025.01.012

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  Compared with last year, ever-growing drilling and testing waste has been created on drilling platforms as the production increase of tight gas is expedited in Tianfu gasfield, which puts forward higher requirements for these platforms in clean production management. Thus, the "1+N" management mode was proposed from three dimensions (personnel quality, professional skill and resource integration), which is conducive to accuracy enhancement in this clean management. Results show that (i) the implementation of the "1+N" supervision under the cooperation of multiple units such as QHSE supervision stations and contractors, with QHSE and well engineering management sectors as the center, can ensure the entire chain of clean production in safe and controllable management; (ii) the "1+N" application achieves the reduction of waste at the source, recycling in the process and harmless treatment at the end, and sets up a "three-waste" treatment system for the clean production; and (iii) the "1+N" process management mode, like optimizing transportation requests, establishing a terminal manufacturer database, and performing supervision in "two stations and one terminal", can achieve the high-quality and high-efficiency management in entire chains of clean production for tight gas.