Hasil untuk "Oils, fats, and waxes"

WANG SHULI, WANG JINGUO, ZHANG CHENGSEN et al.

Accurate interpretation of well logging data is crucial for the evaluation of reservoir fluid properties in oil and gas exploration. Conventional well logging methods rely on petrophysical models that correlate parameters such as porosity, permeability, and oil and gas saturation with reservoir fluid properties to achieve reservoir classification. However, complex geological conditions often lead to issues such as anomalies, multi-factor coupling, and ambiguous fluid boundaries in well logging data. These challenges limit the adaptability of conventional methods and bring uncertainties in interpretation results. To improve the accuracy of reservoir fluid evaluation, this study incorporated cloud model theory into conventional well logging evaluation and proposed an evaluation method for reservoir fluid based on a 2D cloud model. The method selected porosity and gas saturation as key logging parameters and utilized cloud models to process the fuzziness and randomness in well logging data, thereby establishing a mathematical model for reservoir fluid classification. First, a 2D cloud model for well logging evaluation was derived based on cloud model theory, with clarified geophysical significance assigned to its mathematical parameters (expectation, entropy, and hyper-entropy). 2D cloud diagrams of the reservoir were generated using a cloud generator. Subsequently, similarity analysis was applied to quantitatively classify reservoir types, enhancing interpretation accuracy. To validate the effectiveness of this method, well logging data from the Kuqa Depression in the Tarim Basin were used for application analysis, with results compared with those obtained from conventional methods, cloud model evaluation, and well testing. The results showed that the proposed method accurately characterized reservoir fluid properties in complex reservoirs. Compared with conventional methods, the 2D cloud model not only provided qualitative classification of reservoir types but also quantified uncertainties in fluid properties, thus improving the stability and reliability of evaluation results. The findings indicate that the reservoir fluid evaluation method based on 2D cloud model effectively reflects reservoir fluid characteristics and exhibits strong adaptability in complex reservoir environments. The final evaluation results demonstrate strong consistency with well testing results, verifying the method’s feasibility and effectiveness. As a valuable supplement to conventional well logging interpretation, this method provides a new approach for improving the accuracy of well logging data interpretation and optimizing fluid property identification in complex reservoirs.

Li Yong, Xu Zhendong, Wang Chenmin et al.

To solve the problems of low cutting efficiency and unstable cutting fracture quality caused by severe vibration and eccentric rotation of the cutter device in downhole hydraulic cutting operation of tubing and casing， a cutter down-attached anchor tool was developed， which could also realize conventional power up-attachment under special working conditions. The tool uses a rotary seal structure to achieve the “rotation + anchoring” function of the anchor， and solves the problems of small anchoring range and unstable anchoring through blade-type anchor blocks and a dual-piston structure. The field test results show that the down-attached anchor and the hydraulic cutter exhibit excellent operational compatibility. Compared with up-attached anchor cutting operation， the tool string is not eccentric after cutting operation of down-attached anchor， and the overall cutting time is reduced from 4 min to 2 min（ø73.0 mm tubing）， with cutting time shortened by 50%. The down-attached anchor structure can simultaneously anchor at least two sizes of tubing， indicating that it maintains anchoring stability even at larger opening angles. The tool features a simplified and reliable structure， with universal applicability across multiple sizes and working conditions. The successful development of the tool provides guidance for further improving the efficiency of field cutting operations.

J. M. Nazrim Marikkar

Ilfat Z. Rakhmatullin, Sergej V. Efimov, Ekaterina I. Kondratyeva et al.

Application of high resolution 13C nuclear magnetic resonance (NMR) spectroscopy to characterize Cuba oil and oil-containing rock samples from Cuban basin was demonstrated. The chemical shifts of 13C NMR functional groups for later determination the composition of the oil and rock samples were determined. The different contribution of the studied samples in the aliphatic and aromatic areas was determined. Molar fractions of primary, secondary, quaternary, tertiary, aromatic groups, aromaticity factor and the mean length of hydrocarbon chain length of aliphatic hydrocarbons were estimated. Comparative analysis on the quantitative level for all major hydrocarbon components, the aromaticity factor and the mean length of the hydrocarbon chain were carried out.

CHEN Qiang, LI Wenhou, SUN Jiaopeng et al.

The Caojiagou section in Qishan County, Shaanxi Province is located in the southern margin of the Ordos Basin. The well-exposed section deposited complete Ordovician strata and developed various sedimentary types, and its location has convenient transportation. In this paper, the stratigraphy and sedimentary characteristics of the Caojiagou section are introduced in detail. The lower Ordovician Yeli Formation is mainly composed of argillaceous dolomite and Mount Liangjia Formation is characterized by crystal dolomite intercalated with siliceous mass and develops stromatolites, all of which belong to tidal flat facies. The Middle Ordovician Majiagou Formation consists of medium-thin and medium-thick layers of silty-fine dolomite and limestone, belonging to open platform and platform front slope facies deposits. The Fengfeng Formation is mainly composed of medium-thin layer laminated dolomite with a great quantity of thin carbonate debris flow and turbidity current deposits, which represent the gravity flow deposit of the front slope of the platform in the deep-water environment. The Upper Ordovician Pingliang Formation mainly consists of a set of flyschoid rhythmic deposits of the continental slope facies. The Tangwangling Formation represents the debris flow environment of the continental slop and develops the ice-water deposits with typical ice-rafted dropstones.

Xinyu Mao, Nianyin Li, Fei Chen et al.

Abstract In situ heat systems are a technology that effectively solves paraffin deposition and improves oil recovery. Generally, the oxidation–reduction reaction of sodium nitrite and ammonium chloride generates a large amount of heat to promote the melting of paraffin. An in situ heat system combined with an acid-resistant fracturing fluid system can form an in situ heat fracturing fluid system, which solves the problem of the poor reformation effect caused by cold damage during the fracturing process of low-pressure and high-pour-point oil reservoirs. In this paper, with the goals of system heating up to 50 °C, a low H+ concentration, a high exotherm, and reduction of the toxic and harmful by-product NOX, the preferred in situ heat system was found to comprise 1.6 mol/L ammonium chloride, 1.0 mol/L sodium nitrite, and 0.8% hydrochloric acid. The effect of five factors on the heat production of the reaction was studied experimentally, and a reaction kinetic equation for the in situ heat system was proposed based on the results. The results showed that increasing the concentration of the reactants and lowering the ambient temperature produced more heat. The in situ heat system was used to conduct a crude oil cold damage elimination experiment, and the results of the removal experiments verified that the system could effectively but not completely reduce the cold damage. Overall, the in situ heat fracturing fluid system formed by the preferred in situ heat system combined with an acid-resistant fracturing fluid system could avoid cold damage in the formation during construction and increase the output.

ZHENG Lihui, XU Yandong, QIU Ziyao et al.

The analytical method and other qualitative research methods to guide the field leakage prevention and plugging lack of pertinence. Meanwhile, the engineering data used by the quantitative prediction method in the prediction of leakage is incomplete and how to control the leakage quantitatively by adjusting the relevant parameters is not proposed after the loss degree is predicted. In order to solve the above problems, the cocoon stripping algorithm is proposed. Selecting all measurement parameters of 27 of 29 wells in Shunbei Oilfield with average loss rate recorded, and then taking the average loss rate as the objective function, the well depth and drilling and completion fluid density as the independent variables, the multiple linear regression equation is established, and the undetermined coefficients of the equation are solved. Theoretically, T test and F test are used to prove that the equation can meet the requirements of engineering analysis. In practice, the relative error between the calculated value and the actual value of two wells that did not participate in the equation establishment is about 6 %, proving that the equation meets the needs of engineering control. Finally, 17 factors affecting the average loss rate have been screened out by the target equation simplified by the contribution rate method and the cutting element method, among which 10 drilling fluid factors contribute more than 50 %, indicating that a certain average loss rate could be controlled by adjusting the performance of drilling fluid. For the convenience of field control, the performance of drilling fluid is changed by the reading of six-speed viscometer at 300 r/min, so that the main controlling parameters of drilling fluid are reduced to two, which are pH value and the reading of six-speed viscometer at 300 r/min. The minimum average loss is predicted to be 2.3 m³/h through the analysis of the three-element equation. Considering the characteristics of Shunbei block, the leakage in Shunbei oilfield involves geological, engineering, and other operation links is found out through quantitative analysis, and so does the main controlling factors of drilling and completion leakage. By means of cutting elements, contribution rate and other methods, the minimum average leakage rate obtained by controlling the funnel viscosity and the reading of six-speed viscometer at 300 r/min is calculated. In the aspect of guiding the field practice of plugging leakage, it can provide basic data support for the subsequent construction measures to obtain the ideal leak control effect, and provide an optional means for decision-making.

Fernanda Setta, Sérgio Bergamaschi, René Rodrigues et al.

Abstract This assessment of the volumetric potential of the oil shales of Tremembé Formation (Oligocene, Taubaté Basin, Brazil) was based on the sedimentological study of 2457 total organic carbon and 1007 Rock–Eval pyrolysis analyses of core samples from nine survey wells drilled in the central portion of Taubaté Basin. Along a 240-m-thick package in the upper part of Tremembé Formation, thirteen chemostratigraphic units with thicknesses varying from 10 to 35 m were identified. The upper interval (unit L), 30 m thick, exhibited the highest organic content and original generation potential and was thus studied in detail. In unit L, oil yield maps were constructed, seeking to identify the most attractive areas for industrially exploiting the oil shales, and volumetric calculations employing a probabilistic Monte Carlo method were conducted to quantify the potentially recoverable oil volume. Three exploratory scenarios based on yield values (S1 + S2) were considered for calculating the oil volumes, seeking to offer different exploratory scenarios for decision making. For the scenario that considered only average yields above 100 mg HC/g rock, the recoverable oil volume is 525 million bbl (P90) to 884 million bbl (P10); for the scenario that considered only average yields above 80 mg HC/g rock, the recoverable oil volume is 1.4 billion bbl (P90) to 2.6 billion bbl (P10); and for the scenario that considered only average yields above 60 mg HC/g rock, the recoverable oil volume is 3.6 billion bbl (P90) to 5.4 billion bbl (P10).

Santosh Garain, Debashis Mitra, Pranab Das

Abstract Subsurface hydrocarbon traps are not correctly sealed, and hydrocarbons move vertically from the reservoir as invisible traces in the form of microseepages. Long-term hydrocarbon microseepages cause surface or near-surface alterations such as bleaching of red beds, enrichment of ferrous iron minerals and higher concentrations of clay and carbonate minerals in soils/rocks. Multi- and hyperspectral remote sensing data have successfully been used to detect such alterations in many parts of the world. In India, such studies have not been carried out till now. In this study, Landsat 7 ETM+ images have been used to find out hydrocarbon microseepage-bearing areas in part of Assam–Arakan Fold Belt in the northeastern part of India. Based on the spectral characteristics of the hydrocarbon microseepage-induced altered minerals, two spectral enhancement techniques, viz. principal component analysis (PCA) and band ratio analysis, have been carried out on the Landsat 7 ETM+ images. PCA reveals that three principal component images—1457PC3, 1345PC2 and 3457PC4—show relatively better enhancement for the hydrocarbon-bearing alteration areas. Again, band ratio analysis of the images indicates that ratio images—3/1, (2 + 5)/(3 + 4) and 7/5—show excellent spectral enhancement for the hydrocarbon-induced mineral alterations. The three PC images have been combined with the three band ratio images to find out probable hydrocarbon microseepage areas. The remote sensing-derived prospect areas have been validated with surface geochemical, seismic/geologic and gravity data available in the area.

Hao-yu Wang, Junjie Li, Hailong Liu

Abstract This paper presents a new way to calculate productivity of five-spot pattern at high water cut stages. In low permeability reservoirs, it is difficult for the reservoir fluid to flow, and the recovery factor is very low. Being based on the non-Darcy flow in low permeability reservoir, taking threshold pressure gradient into consideration, a new method to calculate the well pattern was built. This method is based on the two-parameter continuous model, and the method of flow line integrals and the numerical integration were used to build the productivity model. Productivity for the new method is validated by comparing with the actual data from field, and both the seepage theory and the reservoir engineering illustrate the correctness of the new method in this paper. The fracture length and pressure difference between the injection well and the production well have a significant effect on the productivity of the fractured five-point well pattern. The greater the length of the fracture is, the higher the productivity of the fractured five-point well pattern is. The greater the pressure difference is, the higher the productivity of the fractured five-point well pattern is.

Cleveland M. Jones

Abstract An analysis of the exploration model that the oil and gas industry currently follows suggests that it often restricts innovation and inhibits exploration efforts. Examples of large, underexplored areas with significant oil and gas potential demonstrate how the current exploration model fails to allow adequate exploration efforts to be conducted. A description of a possible new exploration model is presented, involving the use of exploration technologies already available, as a means of breaking the paradigm of the current exploration model. Results of recent applications of such a model suggest that it can be applied both onshore and offshore, and that it is effective in detecting anomalies associated with significant hydrocarbon accumulations. Employing the new exploration model proposed, it was possible to effectively identify 99% of known hydrocarbon accumulations, although it was most effective at detecting hydrocarbon accumulation anomalies with a linear extent of over 2 km, and it also allowed a valuable ranking of the identified leads. In conjunction with appropriate exploration tools, it reduced exploration risk by avoiding “false alarms,” since it can effectively indicate areas without hydrocarbon potential, even when other geophysical tools would suggest prospectivity. These results suggest that the proposed alternative exploration model can provide a more direct means of assessing the hydrocarbon potential of large exploratory areas, even before other geophysical investigations provide detailed information on possible targets. Breaking the paradigm of the current exploration model may thus be able to shorten the exploration cycle, reduce costs and allow resource development to proceed in frontier regions that would not otherwise be likely to attract exploratory efforts.

Ya DENG, Rui GUO, Zhongyuan TIAN et al.

Abstract: The type, poroperm relationship, log response characteristics and identification criteria of the barriers and intercalations in the carbonates of the Cretaceous Mishrif Formation in the West Qurna oil field of Iraq are studied through comprehensive analysis of cores, thin sections and well logs. The genesis and distribution of the barriers and intercalations are analyzed from the perspectives of sequence stratigraphy, depositional facies and diagenesis. The barriers and intercalations can be classified into three types: grainstone, packstone and wackestone. The barriers and intercalations generally exist in restricted platform facies and evaporative platform facies, some in open platform. They are common in transgressive cycles and early regressive cycles, forming continuously, extensive barriers and intercalations near the sequence boundaries. Penecontemporaneous cementation, burial compaction, and burial cementation led to the decrease of the porosity, damaged the space of the reservoir pores and became the important factors for the genesis of the barriers and intercalations. In the epidiagenetic phase, a large number of CaCO3 precipitated in the phreatic water zone below free-water table, leading to the formation of packstone and grainstone barriers and intercalations in a large scale. Through comprehensive log analysis, log identification criteria and the distribution of the barriers and intercalations are determined. The barriers are mainly distributed in the sections of CRI and CRII, and the intercalations are concentrated in the section of mB1. For different types of barriers and intercalations, packstones are the most in quantity, followed by grainstones and wackestones. Key words: carbonates, barriers and intercalations, geologic feature, genetic mode, log response characteristics, log identification criteria, West Qurna oil field, Iraq

J. B. Nduwayezu, Theoneste Ishimwe, A. Niyibizi et al.

G. Kitanov, D. Karcheva, P. Lukova

E. Pulster, J. Bourgeois, R. Harbison

Cui Yan, Wang Jianjun, Sun Maosheng et al.

During water flooding in offshore oilfields,performances of hydrocycline desanders may directly affect the functioning of filters in later process.This paper presents an analysis on the liquid-solid flow in TP-II-250 hydrocyclone desander through experiment and numerical simulation.Research results show that both the RSM model and DPM model have desirable accuracy in simulation of liquid turbulent flow and solid flow.During the process,pressure drops increased with the increase of feed flow rates.Moreover,the friction between fluid flow and wall and the short-circuiting flow are the two important causes of pressure losses.The tangential velocity and axial velocity are the main velocity components,which can determine the particle separation efficiency of the desander.Hydrocyclone desander can capture all particles with sizes larger than 80μm.The smaller particle sizes are,the easier it is for escaping.As for tiny particles,higher separation efficiency can also be observed due to polymerization and adhesion.With increases in rate of feeding flow,desanding efficiency may increase and then decrease.The feed flow ranges from 56 to 62 m³/h.The highest desanding efficiency can be observed with feeding flow rates at 56-62 m³/h.These results may provide solid foundation for application of hydrocyclone desanders in offshore oilfields for water flooding.

Wu Wenxiu, Deng Kunfa, Xu Fuyan et al.

The derrick will resonate when its natural frequency closes to or coincides with the vibration frequencies of external device and wind load.The theory of modal analysis is introduced.Dynamic analysis on the 450T offshore derrick has been conducted using finite element software to study its vibration characteristics.17 cross-section properties have been defined in modeling based on the material structure of derrick rod.2-node and 188 beam elements are adopted in meshing.The results show that,the prestressing effect will decrease the first 10 order frequency of derrick with insignificant magnitude,indicating a small effect of prestressing on the vibration characteristics of derrick.The corresponding speed of revolution of the former 4 order modal frequency is in the normal range of rotary table and winch revolution speed.But the revolution speeds of the rotary table and winch corresponding to the first and the second order modal frequency,which have close modal frequency values,are less than 100 r/min.

Christoph Herm