Table of Content

01 February 2018, Volume 40 Issue 1

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Two-way Locking Mechanism Design for Telescopic Downhole Tractors

LIU Qingyou, ZHENG Wei, YANG Yaqiang, ZHANG Shuyang, ZHU Haiyan

2018, 40(1):  1-10.  DOI: 10.11885/j.issn.1674-5086.2016.12.24.01

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Design of a two-way locking mechanism for telescopic downhole tractors, based on the principles of self-locking ramps, is reported to improve the traction capacity of telescopic downhole tractors. The proposed mechanism allows the tractor to lock itself to shaft linings in its fore and aft structure, thereby overcoming restrictions in traction force imposed by static frictional forces. This allows the tractor to be towed in both directions while also improving its traction capacity. The twoway lock comprises two locking states:the traction lock and reset lock. Through static-force analyses of both locking states, mathematical relations describing the two-way locking mechanism, when it meets the required locking conditions, were derived. Parametric design of the two-way locking mechanism was performed to ensure that the traction locking state is a self-locking state while the reset locking state is not. Subsequently, a computational model was established to simulate the dynamics of a tractor's frontal working section, thereby completing simulation of two-way locking processes. Results of these simulations have been used to validate the accuracy of the parametric design of the two-way locking mechanism, and the viability of the proposed mechanism has been proven.

Paleontological Features and Sedimentary Environment of Dainan Formation in Deep Sag of Gaoyou Sag

YUAN Jing, XIAO Yunfeng, DONG Daotao, XIONG Guangqin, QIU Yongfeng

2018, 40(1):  11-21.  DOI: 10.11885/j.issn.1674-5086.2016.06.29.02

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Based on rock core and paleontology analyses data, combined with the sedimentary facies, the relationship between fossils, such as ostracods and charophytes, and the sedimentary environment of the first and second members of the fifth sub-member of the Dainan Formation in the Deep Sag of Gaoyou Sag were systematically analyzed. Seventy species of ostracods were identified, with the Cyprididae Baird section molecules being dominant, followed by Candonidae Kaufmann, and a small number of Limnocytheridae. The vertical variation in the fossil assemblage reflects the cyclic changes in the lake water during the Dainan Period, namely, brackish water→fresh water→brackish water→brackish water→fresh water. In addition, 76 species of charophytes were identified, including Grovesichara changzhouensis, S tephanochara fortis, Obtusochara longscoluminania, and Sphaerochara parvula. The first sub-member of the first member of the Dainan Formation is most prosperous, which manifests a quiet and brackish-fresh water environment during those periods. The vertical distribution and evolution of the ostracods and charophytes fossil combination has a close relationship with the changes in and distribution of the sedimentary environment and facies. When the ostracods fossil assemblage in fresh to brackish water is in a dominant position and the chara is flourishing, it indicates that terrigenous clastic sediment is abundant. Additionally, the sedimentary facies are dominated by aggradation or a progradation delta and fan delta. When the ostracods fossil assemblage in brackish water is in a dominant position, it indicates that the terrestrial sources are short of clastic substance supply, and the retrogradation delta and fan delta are the main sedimentary facies.

Analysis on the Characteristics and Variations of Member 1 of the Qingshuihe Formation in the Luxi Region

WANG Jian

2018, 40(1):  22-34.  DOI: 10.11885/j.issn.1674-5086.2016.07.12.62

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To elucidate the reservoir characteristics and controlling factors of Member 1 of the Qingshuihe Formation (Qingshuihe Member 1), which lies to the west of the Luliang uplift, and to guide the prospecting of "sweet spots" in the reservoir, a comparative analysis between the sandstone and glutenite reservoirs of Qingshuihe Member 1 was performed through the analysis of a large numbers of rock thin-sections and casting thin-sections via scanning electron microscopy and X-ray diffraction, combined with the analysis of rock core observations, petrophysical properties, and mercury porosimetry. Significant differences were found between the microscopic and macroscopic characteristics of these reservoirs. (1) Sandstone reservoirs are mainly comprised of medium-to-fine grained feldspar lithic sandstones that are primarily distributed within the northwestern side of the research area, whereas glutenite reservoirs are mainly composed of fine conglomerate and sandy fine conglomerate that are mainly distributed in the northeastern side of the research area. (2) Reservoir spaces in sandstone are mainly comprised of primary pores, with plagioclase dissolution pores supplementing these spaces, whereas the main reservoir space in glutenite is comprised of intergranular calcite dissolution pores. (3) The average porosity of sandstone and glutenite reservoirs are 14% and 11%, respectively, indicating that sandstone reservoirs have better petrophysical properties than glutenite reservoirs. However, glutenite reservoirs have better pore-throat structures, as most of their pores are large and have coarse skewness. (4) Sandstones are strongly affected by compaction. The tectonically elevated Hedao sandstones in the north (e.g. the Xiayan-8 well) experienced weaker levels of compaction due to their shallow burial depths, and thus have better petrophysical properties. Intense carbonate cementation during the early stages of glutenite reservoir development led to the compaction of these reservoirs, and the petrophysical qualities of these reservoirs are determined by the effects of dissolution around locations where such faults developed.

A Study on the Characteristics and Factors Affecting Volcanic Reservoirs in the Suhongtu Formation of the Chagan Depression

YANG Yuping, ZHU Xiaomin, GUO Dianbin, LIU Xuan, GONG Zhuangzhuang

2018, 40(1):  35-46.  DOI: 10.11885/j.issn.1674-5086.2016.07.06.04

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The reservoir characteristics of the Suhongtu Formation in the Chagan Depression were studied using rock cores, thin sections, scanning electron microscopy, and mercury intrusion porosimetry in combination with well logging and seismic data, to identify the main factors affecting reservoir performance. Results of this study indicated that the primary reservoir spaces in volcanic rocks are gas pores, fractures, dissolution pores, dissolution fractures, and microscopic pores and fractures. Basalt gas pores, fractures and dissolution pores were broadly developed and distributed, and basalt is the main type of reservoir rock in the research area. Tuff fractures were also relatively well developed and were second only to basalt in terms of distribution, thus making tuff the second most important type of reservoir rock in the research area. The later the volcanic rocks are formed, the better is the preservation of their primary porosity and fractures. The explosive-effusive facies transition zone and parts of the upper section of the effusive facies have good petrophysical properties, and the filling of gas pores and fractures were the main cause of petrophysical degradation in volcanic rocks. Tectonic fractures and their associated weathering-induced leaching and dissolution greatly improved the reservoir performance of volcanic rocks. The clays generated during the alteration of volcanic minerals not only clog pore openings and degrade petrophysical properties, but also reduce the density of the rocks. These actions thus created the conditions for dissolution and alteration in subsequent periods.

The Characteristics and Main Controlling Factors of Tight Oil Reservoir Formation in the Wolfcamp Series of the Permian Basin, USA

SUN Xiangcan, TONG Xiaoguang, ZHANG Guangya, WEN Zhixin, WANG Zhaoming

2018, 40(1):  47-58.  DOI: 10.11885/j.issn.1674-5086.2016.07.22.01

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We conducted a deep analysis of the Wolfcamp Series tight oil reservoir formation conditions and discuss the main controlling factors of tight oil reservoir formation based on the analysis of the structural and sedimentary characteristics and systematic research on hydrocarbon source rock and reservoirs in the Wolfcamp Series of the Permian Basin. The results show that the Wolfcamp Series has good geological conditions for tight oil enrichment:excellent hydrocarbon source rocks that consist mainly of siliceous and calcareous shale and excellent " bottom-generating, top-storing" source-reservoir configuration. The main factors controlling the tight oil production and distribution are the source rock and reservoir characteristics and the source-storage configuration. The hydrocarbon source rock characteristics are the primary controlling factor because they determine the abundance of resources; the reservoir characteristics and good source-storage configuration determine the tight oil production, migration method, and hydrocarbon removal efficienc, and are crucial for the tight oil accumulation.

Evolution and Quantitative Delineation of Fluvial Channel Sandbodies in Block SA of the South Turgay Basin, Kazakhstan

GUO Kai, ZHAO Ruichun, FAN Leyuan, HU Shengli, LI Yang

2018, 40(1):  59-67.  DOI: 10.11885/j.issn.1674-5086.2016.08.09.01

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Effective delineation and evaluation of fluvial channel sandbodies are impeded by their rapid lateral variations. In this study, frequency detection, phasing, stratal slicing, geological engraving, and other techniques were comprehensively applied to study the characteristics and duration of channel development in the Upper Jurassic Akshabulak Formation, located in Block SA of the South Turgay Basin. First, the possible existence of two stages of channel sedimentary bodies with different tuning thickness was detected within the target segment using the frequency-division method. Next, wave impedance analysis and 90° phase conversion revealed relatively good agreement between the seismic negative amplitude of the target segment and channel sands. Lastly, based on a high-frequency sequence stratigraphic framework, two types of channel sands from different stages were identified and delineated using isochronous stratal slicing; single-well calibration analysis of the characteristics of channel sedimentation were combined with the amplitudes of typical stratal slices. A comprehensive analysis of various parameters, including channel sinuosity, width-thickness ratio, and reservoir volume, suggests that the early-stage channel had characteristics of a meandering river with low sinuosity. In contrast, the late-stage channel was a delta plain distributary channel, with the characteristics of a flat, straight river. In addition, the channel had a significantly higher reservoir volume in the early stage compared to the late stage.

Study on the Classification and Modeling of Fracture-Vug Oil Deposits

LÜ Xinrui, HAN Dong, LI Hongkai

2018, 40(1):  68-77.  DOI: 10.11885/j.issn.1674-5086.2016.07.21.03

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To characterize the various types, scale differences, and spatial distribution features of fracture-vug carbonate reservoir systems, we used the "classifying, categorizing, karst-facies control, multi-type integration" method and modeled the respective scales, external morphology, and internal attributes of various types of fracture-vug reservoir systems. Based on the karst origin integration principle, we integrated various types of fracture-vug reservoir systems and verified the model reliability through well drilling. The results show that this method is suitable for the geological modeling of such highly heterogenous reservoirs and can effectively characterize various reservoir systems and the spatial distribution of their parameters. Based on the model, the reserve composition of unit XX was refined; the karst cave reserves made up 63.1%, the dissolved pore reserves accounted for 34.5%, and large-scale fracture reserves accounted for 2.4% of the unit. The model simulation of oil deposit numerical values obtained better fit and simulation results.

Geological Information Analysis of Horizontal Wells and 3D Modeling of Shale Gas Reservoir

QIAO Hui, JIA Ailin, WEI Yunsheng

2018, 40(1):  78-88.  DOI: 10.11885/j.issn.1674-5086.2017.05.10.04

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Shale gas exploration is characterized by short evaluation periods and few evaluation (vertical) wells. The low density of vertical wells for evaluation aggravates technical difficulties in detailed reservoir description and geological modeling. Therefore, this study established a quantitative identification standard for the lithological, physical, and electrical properties of the study area. This standard was used to carry out fine stratigraphic division of horizontal wells and sections, as well as performing stratum thickness corrections during actual drilling, to transform horizontal wells and sections into vertical wells with multiple laterally arranged openings. On this basis, data extracted from each layer of the horizontal section were used as control points to establish a detailed structural model of the study area. In the multiple-point geological information analysis, horizontal sections were considered multiple-opening evaluation wells to obtain relevant geological parameters, effectively compensating for the lack of data in evaluation wells.

A Study on Nuclear Magnetic Resonance to Reservoir Quality Evaluation

ZHAO Jianbin, WAN Jinbin, LUO Anyin, CHENG Daojie, LI Huiying

2018, 40(1):  89-96.  DOI: 10.11885/j.issn.1674-5086.2016.08.04.02

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In view of the difficulties in evaluating the quality and assessing the productivity of low-permeability complex porestructure clastic rock reservoirs with medium to low porosity located in the middle and deep formations of the central Hebei Area, we initiated a study involving the quantitative characterization of the pore structure based on nuclear magnetic resonance spectroscopy. By combining the well testing analytical data, we determined the correlation between the lower reservoir quality limit and index and the reservoir fluid production, established an appropriate reservoir classification standard for the area, and developed a well-rounded reservoir quality and productivity evaluation technique. The application of this technique to the evaluation of reservoir effectiveness and productivity showed good results; with the high accuracy rate of 87.7%, it can provide accurate suggestions for well testing in oil field exploration and development.

A New Method of Explaining the Water Saturation of Low Resistivity Reservoir with Complex Pore Structure

ZHANG Hengrong, HE Shenglin, ZHENG Xiangwei, HU Xiangyang, ZENG Shaojun

2018, 40(1):  97-103.  DOI: 10.11885/j.issn.1674-5086.2016.06.26.01

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The gravelly sandstone reservoirs of the Liusha Formation in Wushi, Beibu Gulf are subject to complicated changes in lithology, sorting and distribution of pore throats, the resistivity of the oil layer is lower than that of the mudstone and is similar to that of the water layer, the porous tube microstructure model was used to simulate the response of pore structure and rock resistivity. It is proved that the complex pore structure of rock is an important reason for the formation of peculiar low resistivity reservoir of gravel sandstone. The Archie correction equation is proposed based on experimental "bent" rock electrical data caused by complex pore structures. The modified Archie formula is applicable to reservoirs with different pore structures. The Wushi A Oilfield gravel sandstone reservoir is evaluated by a new method, can effectively improve the oil saturation, and the results are more compatible with core capillary pressures and NMR-bound water.

New Epidermal Model of Partially Perforated Deviated Well in Anisotropic Reservoir

DONG Wenxiu, WANG Xiaodong, WANG Jiahang

2018, 40(1):  104-113.  DOI: 10.11885/j.issn.1674-5086.2016.10.11.06

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In order to study the yield-increasing effect of partially perforated deviated wells, the point sink solution in the infinite plate reservoir with closed top and bottom boundaries is obtained through mirror image inversion and then superposition of the spatial instantaneous point sink solution; then, the solution of the partially perforated deviated well is obtained by integration along the deviated well trajectory; finally, a new epidermal model of a partially perforated deviated well is acquired through the late approximation of the pressure solution. The validity of the new epidermal model is verified through comparison with previous models of deviated wells and a partially perforated well epidermis separately. The results show that the epidermal factor gradually decreases with the increase in the deviation angle and bore length of the well; the yield-increasing effect produced by the well deviation angle increase would be more obvious if the well bore length increases; the increase in the anisotropic factors of reservoir thickness and permeability would reduce the yield-increasing effect. Moreover, the well deviation angle increase would make the epidermal factor decrease significantly in the reservoir with smaller anisotropic factors of permeability, in which the partially perforated deviated well with a larger deviation angle and well bore length would have a better yield-increasing effect.

Model for Capacity Forecasting of Thermal Soaking Recovery in Horizontal Wells in Heavy Oil Reservoirs

MA Kuiqian, LIU Dong

2018, 40(1):  114-121.  DOI: 10.11885/j.issn.1674-5086.2016.11.09.02

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To address the lack of a suitable calculation model for productivity prediction of thermal soaking recovery in horizontal wells in conventional heavy oil reservoirs, by establishing composite geological model including heating zone and unheated zone and considering the difference of crude oil viscosity between the heating and unheated zones, an analytical model describing the production capacity of thermal soaking recovery in a single horizontal well was determined. Further, an equation for calculating the productivity increase of thermal soaking recovery with respect to cold recovery was proposed. The results show that the productivity multiple is mainly affected by factors such as the heating radius, oil layer thickness, and horizontal section length. Based on typical thermal recovery data in horizontal wells in the Bohai N oilfield, a mechanistic model was established. The heating radius of different soaking cycles was obtained by numerical simulation. On this basis, the increase of production capacity in different soaking cycles was calculated by the new model. It is predicted that the productivity increase of the first soaking cycle was 1.6 times, which was in good agreement with the evaluation results of the first thermal soaking cycle in the ten thermal soaking recovery horizontal wells at the Bohai N Oilfield.

Novel Algorithm for Calculating Ideal Gas Phase Reactions Based on the Minimization of Free Energy

ZHANG Shouxin, ZHANG Zubin

2018, 40(1):  122-129.  DOI: 10.11885/j.issn.1674-5086.2016.10.08.01

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In this work, we propose a gradient projected Lagrangian algorithm to address the inadequacies of current free-energy minimization-based solution method for calculating the composition of the ideal gas phase equilibrium. In this algorithm, a weak convergence criterion was used as the convergence criterion of the gradient projection method. Mathematical proofs were then provided for the rationality of the weak convergence conditions used in the gradient projection method, as well as the convergence of this algorithm. On this basis, the result calculated by the gradient projection method was used as the initial value in Newton's method with Lagrange multipliers, and improvements were also made on the iteration step used in Newton's method. We have thus resolved the difficulty of selecting an initial value for Newton's method, and improved the stability and computational speed of the algorithm. The results of example calculations demonstrated that the algorithm proposed in this work converges very quickly and exhibits a high level of computational accuracy.

Study on Interlayer Parameters of Bottom Water Heavy Oil Reservoir Under Single-well Condition

HUANG Shijun, SONG Qianlan, CHENG Linsong, YANG Yang, ZHOU Zhonghao

2018, 40(1):  130-140.  DOI: 10.11885/j.issn.1674-5086.2016.09.20.01

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The main problem during the production of bottom water heavy oil reservoirs is the imbibition of the bottom water. The use of horizontal wells can effectively alleviate this production contradiction. At the same time, the existence of the interlayer can greatly reduce the rise of the bottom water, improve the recovery extent, and improve the recovery efficacy. This paper discusses the effect of the change of interlayer parameters on the production under the condition of a single well. There are many interlayer factors affecting the recovery efficacy. According to research, and considering the typicality and feasibility, three parameters, including the interlayer dimensionless area, interlayer dimensionless vertical position, and interlayer permeability, were selected for the study of the effect of interlayer parameters on production efficacy. Based on the actual parameters of the Bohai A reservoir, the numerical model of the bottom water heavy oil reservoir with interlayer was established. The production curve, water saturation rising curve, streamline field model diagram, and saturation field diagram were analyzed by the reservoir engineering method. The effect of each single factor on the production was studied:a larger interlayer corresponded to better production. The closer the interlayer is to the oil-water interface, the better the production is. The production in the case of an interlayer with low permeability is better than that in the case of a barrier. Based on the single-factor influence analysis, the orthogonal experiment was carried out, and the influence due to multiple factors was analyzed. The influence degree of the three interlayer parameters was determined. In decreasing order of influence, the parameters are:interlayer dimensionless area, interlayer dimensionless vertical position, and interlayer permeability.

Study on Patterns of Change in Oil Reserve Permeability During Microfracturing of SAGD Wells

CHEN Sen, LIN Botao, JIN Yan, ZHANG Lei, HUANG Yong

2018, 40(1):  141-148.  DOI: 10.11885/j.issn.1674-5086.2016.06.21.05

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In steam-assisted gravity drainage (SAGD) wells containing superheavy oils, reservoir microfracturing will quickly establish a connection between the upper and lower horizontal wells, thus improving initiation efficiency. To understand the changes in permeability of microfractured reservoirs and to assess the efficacy of microfracturing processes, we measured the porosity and permeability parameters of oil sand reservoirs with different physical properties from the Fengcheng oilfield in Xinjiang, and studied how the pore volume, anisotropy, and temperature of the oil sands affected their permeability. The experimental results indicated that the variations in absolute permeability and effective water permeability of these sands with their porosity or volumetric strain are consistent with the Kozeny-Carman (or Kozeny-Poiseuille) equation, regardless of whether the sands were in their in situ or shear-dilated states. The absolute permeability of the sands in the horizontal direction was found to be greater than that in the vertical direction, whereas the opposite was observed for effective water permeability. Meanwhile, the injectant temperature in microfracturing processes appears to have a negligible impact on effective water permeability. On this basis, the differences in seepage during microfracturing and cyclic steam injection were investigated from a mechanistic perspective, with the use of finite-element analysis. It was shown in case calculations that microfracturing simulations should be performed using the effective water permeability.

Effects of Injection Pressure on Gas Channeling during CO₂ Flooding and a Study on Sealing of Cracks

SHI Lihua, DANG Hailong, KANG Shengsong, WANG Weibo, WANG Qiang

2018, 40(1):  149-156.  DOI: 10.11885/j.issn.1674-5086.2016.05.29.03

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To determine the impact of injection pressure on gas channeling during CO₂ flooding processes, different injection pressure schemes were set up according to actual oil recovery conditions, through which the breakthrough times with different injection pressures were measured. From this experiment, we obtained the variation of CO₂ breakthrough velocities and recovery rates with injection pressure. The results indicated that injection rate, base substrate permeability, and the size and width of cracks are the most important factors for injection pressure, and the selection of an appropriate injection rate was the key for controlling injection pressure. It was found that the injection pressure increased in proportion with the injection rate, decreased with increases in the size of the cracks, and decreased with increases in base substrate permeability. These results showed that the optimal injection rate for starch systems was 0.2 mL/min. In crack simulation experiments using rock cores, the sweep volume of a gaseous body was significantly affected by cracks in the reservoir, as the recovery rate falls below 1% for differentials larger than 1 000. The composition of the optimal high-strength gel system was:4% starch + 4% monomer + 0.05% crosslinking agent + 0.18% antigumming agent. This gel system has high strength, a gelling time between 8 and 20 h, and stable performance; hence, it is capable of sealing cracks effectively. The recovery rate reached 19% after crack sealing was performed using this gel, thus demonstrating that this gel system effectively increased the sweep volume of CO₂ flooding.

Effects of Polymer Rheology on Sweep Efficiency of Heterogeneous Oil Reserves

HU Ke, XUE Xinsheng, KANG Xiaodong, FENG Rusen

2018, 40(1):  157-164.  DOI: 10.11885/j.issn.1674-5086.2016.08.29.01

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Studies on the relationship between polymer solution rheology and the seepage characteristics in heterogeneous oil reserves provide a useful theoretical basis to improve the efficacy of polymer flooding in offshore oilfields. On the basis of the actual heterogeneity of heavy oil reservoirs in the sandstones of an offshore oilfield, we developed a two-dimensional visual sand-packed model capable of simulating reservoir heterogeneities in the seepage of oil displacement systems within the deeper parts of an oil reservoir, under high pressures. In this work, we performed a rheology experiment using injections with a fixed shear rate on three oil displacement systems. These displacement systems have significantly different rheologies, but similar shear viscosities at the same shear rate. It was shown in this experiment that oil displacement using these three oil displacement systems always resulted in wedge-shaped residual oil distributions within the similitude model. However, there were significant differences between these systems in their transparent areas and seepage patterns. It was shown that polymer solution rheology can delay the onset of ineffective cycling during fluid injections, thus improving the sweep efficiency of oil displacement in low-permeability reservoirs, resulting in increases in sweep efficiency with decreases in the power law exponent, n.

Selection, Evaluation, and Formulation of Drying Agents for Tight Sand Reservoirs

XIONG Yu, MO Jun, LI Peisi, ZHANG Liehui, JIANG Qian

2018, 40(1):  165-172.  DOI: 10.11885/j.issn.1674-5086.2017.04.11.01

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Tight sand gas reservoirs generally have relatively high levels of water saturation in their original state, and tests have shown that the permeability of dry cores is more than 10 times higher than that of the original water-containing cores. In addition, various water-based working fluids will seep into a formation upon contact with the reservoir, which leads to liquid phase retention. This increases the water saturation of matrices near the well or fracture plane, thereby further decreasing the gas phase permeability of the reservoir and greatly reducing its productivity. To solve this problem, we developed a reservoir drying agent called "ACHM". We first experimentally evaluated drying agents by measuring the depletion of formation waters after injecting the drying agents. Chromatography and X-ray diffraction (XRD) methods were also used to analyze the gases produced by the reactions between the drying agent and water, and the composition of their residues. The experimental results indicate that ACHM has a delay in its reaction time that is inversely proportional to the temperature. The water consumption of the drying agent is not affected by the type and salinity of the formation waters, and the optimal molar mixing ratio of the two drying agents was 0.25.

Study on the Quality Evaluation of Electric Submersible Pumps Based on Improved K-means

LIU Guangfu, ZHU He, ZHOU Kaidi, JIAN Jixin, CHANG Yunfei

2018, 40(1):  173-180.  DOI: 10.11885/j.issn.1674-5086.2016.11.25.02

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This study examines issues concerning the lifespan of electric submersible pumps and establishes assembly quality grade classifications based on underground vibration measurements. A 3D vibration model of a single electric submersible pump is established. The inflection point method is proposed to optimize the selection of the initial point for a K-means clustering algorithm. 3D synthetic method is employed to calculate the root-mean-square of the synthetic vibration acceleration in three dimensions. The improved K-means algorithm is used to perform a cluster analysis on the root-mean-square values of the synthetic vibration acceleration for 239 electric submersible pumps. Evaluation criteria for the assembly quality of electric submersible pumps are established. Quality tracking is carried out for electric pump measurements and the research results verify the rationality of the established classifications for electric pump assembly quality. According to the results, electric submersible pumps with root-mean-square synthetic vibration accelerations smaller than 1.30 m/s² are excellent pumps with the longest life spans. These pumps are applicable for use in high-yield wells. Pumps with values between 1.30 and 1.72 m/s² are considered as having good quality. Pumps with values between 1.72 and 2.35 m/s² have a typical lifespan and should be used carefully. Those with values higher than 2.35 m/s² are poor quality pumps with a short lifespan and should be repaired before use.