Water Absorption Profile Research Articles

Evaluation and regulation methods for the utilization of Type-II oil reservoirs using ASP flooding

Abstract Existing methods for calculating oil reservoir utilization in chemical flooding rely on the instantaneous water absorption profile, which fails to provide an accurate description of the actual utilization conditions of the reservoir, making it imperative to find a method that accurately reflects the reservoir utilization. Type-II oil reservoirs often exhibit significant vertical heterogeneity. During chemical flooding, the impacts of high-permeability layer utilization, low-permeability layer utilization, and the simultaneous utilization of both layers on recovery are to be explored. Therefore, it is important to investigate the recovery requirements for different types of reservoirs. This study explores the solutions for improved reservoir utilization as well as the evaluation and regulation methods for the utilization of secondary oil reservoirs using the Alkaline-Surfactant-Polymer (ASP) flooding, which is of great significance for the adjustment of ASP flooding, injection, and production of secondary oil reservoirs.

Preparation and Performance Evaluation of Self-Cementing Nanoscale Polymeric Microspheres with Salt and Temperature Tolerance.

Polymer microspheres with temperature and salt resistance were synthesized using the anti-suspension polymerization method, incorporating the functional monomers AMPS, AM, and AA. To enhance their self-gelling properties, the microspheres were designed with a core-shell structure. The shell is composed of a polymeric surfactant, fatty alcohol polyoxyethylene ether methacrylate (AEOMA), which serves as a thermosensitive crosslinking agent, enabling self-crosslinking upon shell decomposition, addressing compatibility with reservoir pore throat dimensions. Comprehensive characterizations including infrared spectroscopy, scanning electron microscopy, optical microscopy, and laser particle size analysis were conducted. The microspheres exhibited successful synthesis, a nanoscale size, and regular spherical morphology. They demonstrated excellent temperature and salt resistance, making them suitable for high-temperature, high-salinity reservoir profile control. With a stable three-dimensional network structure, the microspheres displayed good expansion behavior due to hydrophilic groups along the polymer chains, resulting in favorable water affinity. Even after aging, the microspheres maintained their gelling state with a distinct and stable microscopic network skeleton. They exhibited superior plugging performance in low-permeability reservoirs, while effectively improving water absorption profiles in reservoirs with permeability contrasts of 10 to 80, thereby enhancing oil recovery.

A prediction model for water absorption in sublayers based on stacking ensemble learning method

The water absorption profile can reflect the difference in the waterflooding status of each sublayer in the injection well, and predicting the water absorption profile has important guiding significance for formulating and adjusting the waterflood development plan. Currently, numerical simulation and radioisotope logging techniques are commonly used to obtain the water absorption in sublayers. However, the complex and increasingly heterogeneous subsurface formations in China's oilfields have made it impossible for the numerical simulation to reflect the actual reservoir water injection status by splitting the water absorption into sublayers. Although the radioisotope method is more accurate, it is more expensive and has less actual test data in oilfields. In addition, the water absorption prediction model built by traditional machine learning only applies to injection wells with a small amount of water absorption profile data, and its prediction accuracy needs further improvement. In this paper, a new machine learning prediction method is proposed to build a water absorption profile prediction model by stacking ensemble learning algorithm, which achieves the prediction of water absorption in sublayers for injection wells without historical data of water absorption profiles during the development period. In our model, based on the oilfield's static geological data and dynamic production data, the input feature parameters are comprehensively selected by a hybrid feature selection method to analyze the importance of each feature. The robust base-learners are extracted from the sub-model pool by comparing and analyzing the comprehensive prediction performance of each individual model, including ANN, KNN, SVR, RF, XGBoost, LightGBM, etc. The stacking ensemble model was trained using K-fold cross-validation on a randomly divided dataset, which improves the predictive performance of an individual model by combining the advantages of multiple base-learners so that it can accurately reflect the dynamic changes of the water absorption profile. Finally, a case study from the MG study area of the DG oilfield was conducted to verify the model's predictive effect. This case shows that the stacking model proposed in this paper has better performance in predicting the water absorption in sublayers compared with the traditional single model and other ensemble models, and the model has a strong generalization ability, which proves that the method can be used in studying the prediction of the water absorption in sublayers of injection wells.

Effects of biogenic sulfuric acid on simulated concrete septic tanks

Concrete is the major construction material for infrastructure development. Concrete sewer septic tanks are Constructed using the conventional ordinary portland cement (OPC) and the Portland pozzolana cement (PPC). However, OPC based concrete sewer systems are susceptible to biological, mechanical, and chemical degradation. Degradation of the concrete septic leads to their failure hence imposing tremendous environmental problems. The aftermath is the emergence of sanitation-related diseases. The wastewater from failing septic systems leads to contamination of the groundwater or the surface water resulting in the pollution of drinking water. Therefore, the need to explore other possibilities and potential construction materials to achieve sustainable sanitation is inevitable. The use of Limestone Calcined Clay Cement (LC3) in the construction of degradation-resistant concrete sewer septic systems has not been well explored in Kenya. LC3 concrete is resistant to the deterioration effects of aggressive media such as acids, chlorides, and sulfates. This paper presents experimental performance and findings of LC3 in aggressive media vis a vis OPC. The LC3 was formulated by mixing clinker, Calcined clay, limestone, and gypsum at percentages of 50 %, 30 %, 15 %, and 5 % respectively. Compressive strength, Sorptivity, and weight loss during the wet and dry cycles for both LC3 and OPC were evaluated. Simulated concrete septic tanks made of LC3 and OPC were made by casting cubes at water cement ratio of 0.5 and cured in fresh water at ambient temperature for 28 days. These cubes were passed through a regime of W-D cycles in the 3% concentration of Biogenic sulfuric acid. It was observed that after 28 days of curing OPC cubes had slightly higher compressive strength than LC3. However LC3 concrete cubes are expected to have higher compressive strength than the OPC. Cubes curing time increases due to increased pozzolanic activity. Biogenic sulphuric acid attacks on hydrated cement products cause a decrease in compressive strength. The water absorption profile of LC3 cubes was lower as compared to OPC cubes. In conclusion, LC3 cubes had a high potential of resisting degradation as compared to OPC cubes. LC3 show more impressive performance, hence LC3 It’s a potential binder for use in the construction of sewer system.
 Keywords: Septic tank, Sorptivity, compressive strength, wet-dry cycles, biological, mechanical, and chemical degradation, sustainable sanitation, LC3.

Applied development of sustainable-durable high-performance lightweight concrete: Toward low carbon footprint, durability, and energy saving

Over the past few decades, the utilization of Lightweight Concrete (LWC) has emerged as a promising solution for reducing the dead load of structures. However, a key concern associated with the reduction of concrete density, is the potential decrease in mechanical and durability properties. This paradox necessitates a precise mix design that fulfills the requirements of high-strength concrete. This article investigates the influence of Lightweight Expanded Clay Aggregate (LECA) on the strength and durability, and thermal conductivity of Lightweight High-Performance Concrete (LWHPC). The LWHPC mixes explored in this study include sustainable cement solutions such as Portland limestone cement, varying water/binder ratios of 0.3 and 0.35, Leca contents ranging from 5 % to 20 % by volume, and two different pozzolanic supplements, namely silica fume and fly ash, which can be reducing porosity and enhancing durability and mechanical strength. The durability properties of the concrete were assessed through water absorption, electrical resistivity, and chloride migration profiles. Additionally, thermal conductivity measurements were conducted on all specimens. The results indicate that LWHPC, with a lower water/binder ratio, exhibits higher compressive strength and lower absorption, indicating good concrete quality. Generally, after a curing period of 90 days, mixtures with a density exceeding 1700 kg/m3 demonstrated superior durability characteristics. Furthermore, LWHPC mixes in both water/binder ratio groups displayed significantly low thermal conductivity with increasing lightweight aggregate content.

Experimental Study on Enhanced Oil Recovery of the Heterogeneous System after Polymer Flooding

Daqing Oilfield faces increasing reservoir heterogeneity after years of polymer flooding, limiting further enhanced oil recovery. A novel preformed particle gel (PPG) was developed by Daqing Oilfield due to the limited profile control ability of polymer flooding. The preformed particle gel possesses strong deformation ability and the ability to pass through pore throats. The PPG was developed considering the in situ reservoir conditions and combined effects of plugging and flooding. Thus, a heterogeneous system was prepared by mixing polymers and the PPG. In this study, we measured the related properties of the system and assessed its profile control ability and oil displacement performance after polymer flooding. The experimental results demonstrate that typical polymer flooding cannot improve oil recovery under current reservoir conditions. Thus, deep profile control technology should be applied to remediate the highly heterogeneous reservoir issue. PPG can considerably increase the viscosity and stability of the system. The heterogeneous system has a strong plugging ability during the subsequent water flooding stage and is suitable to inject into the medium and high permeability layers. The water absorption profile of the core samples is significantly improved due to the impact of the PPG on the plugging of the layer with high permeability and the liquid flow direction. The system displays an excellent profile control effect in the core with a permeability ratio (high permeability/low permeability) of two under the conditions of a PPG concentration of 500 mg/L and an injection volume of 0.5 PV. In the oil displacement experiment, the recovery efficiency was raised by 16.56% using the polymer system, leading to significant swept volume increment and oil recovery improvement.

Statistical Analysis of Changes in Physical and Chemical Parameters and Cooking Quality of Rice with a Combination of Temperature Treatment and Amylose Content During Storage

Rice is one of the staple foods produced in Indonesia. One of the postharvest processes experienced by rice is storage. During the storage process, rice changes cooking quality, physical and physicochemical qualities. This research aims to analyze changes in cooking, physical and physicochemical qualities of Indonesian rice varieties. The rice varieties used, namely Sintanur, Ciherang, and IR 42 were stored at storage room temperatures of 30˚C, 20˚C, and 10˚C. Rice taken from farmers was stored for 4 months and changes were measured for parameters of water content, color (chroma, hue, whiteness), amylose, elongation ratio, gel consistency, alkali spreading value (ASV), water absorption, and texture profile (packability, hardness, cohesiveness, extrudability, chewiness). The results showed that the lowest water content was at sintanur which was stored at 10 ˚C, namely 3.09% wb, elongation, and ASV increased with the highest final value at sintanur 30 ˚C, namely 2.07 and 4.45, the consistency of the gel decreased in the first week then stable in the following week, on the other hand, water absorption increased at the beginning of storage and did not change much until the end of storage. Statistical tests showed that there was an interaction between time*variety*temperature on the parameters of water content, whiteness, elongation ratio, water absorption, amylose, and chewiness. Based on the research results, it was found that several parameters did not interact with temperature, namely hue, packability, hardness, and extrudability. Keywords: Amylose content, Cooking quality of rice, Physical quality of rice, Rice storage

Preparation and Performance Evaluation of a Temperature and Salt Resistant Hydrophobic Associative Weak Polymer Gel System.

We targeted high-temperature and highly saline old oil fields, whose environmental conditions could be attributed to the significantly high heterogeneity cause by long-term water flooding. The Huabei Oilfield was chosen as the research object. We developed a hydrophobic functional monomer-polymer with temperature and salt resistance by introducing the temperature-resistant and salt-resistant monomer NVP and a hydrophobic functional monomer into the main chain for copolymerization. We used a crosslinking agent with phenolic resin to prepare a weak gel system that showed temperature and salt resistance and investigated its temperature and salt resistance, infective property, plugging performance, liquid flow ability, micropore throat migration, and plugging characteristics. The results obtained using the infrared spectroscopy technique revealed the successful preparation of the phenolic resin crosslinker. The weak gel exhibited good temperature and salt resistance when the polymer concentration was 2000 mg/L, the cohesion ratio was 1:1.5, the additive concentration was 2000 mg/L, the reservoir temperature was 120 °C, and the injected water salinity was 40,300.86 mg/L. The average viscosity retention rate of the 90-day weak gel reached more than 80% and its microstructure was examined. The coreflow experiment results revealed that the weak gel system was characterized by good infectivity. After plugging the weak gel, the effect on the direction of the liquid flow was evident and the flow rate of the low permeability layer increased to a maximum of 48.63% under conditions of varying permeability levels. A significant improvement in the water absorption profile was achieved. The plugging was carried out through a sand-filling pipe under varying permeability conditions and the pressure measuring points in the sand-filling pipe were sucessfully pressurized. The migration ability of the weak gel was good and the blocking rate was >85%.

Production characteristics and displacement mechanisms of infilling polymer-surfactant-preformed particle gel flooding in post-polymer flooding reservoirs: A review of practice in Ng3 block of Gudao Oilfield

The pilot test of infilling polymer-surfactant-preformed particle gel (PPG) flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China. However, the production characteristics and displacement mechanisms are still unclear, which restricts its further popularization and application. Aiming at this problem, this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves, including W-type, U-type, V-type response, and no response. Furthermore, the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency. The overall sweep efficiency of gradual-rising W-type, gradual-decreasing W-type, and early V-type response increases from 0.81 to 0.93, 0.55 to 0.89, and 0.94 to 1, respectively. And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425, and 0.0677 to 0.1654, respectively. Then, the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics, namely disconnected remaining oil, streamline unswept remaining oil, rhythm remaining oil, and interlayer-controlled remaining oil. Furthermore, the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile. Generally, improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil. The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil. The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil. Finally, the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding. The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.

Dynamic Evaluation of Flow Unit Based on Reservoir Evolution: A Case Study of Neogene Guantao Ng3 Formation in M Area, Gudao, Bohai Bay Basin

To clarify the dynamic evolution characteristics of reservoir flow units during water injection development, the upper member of the Neogene Guantao formation in Block M of Gudao Oilfield is taken as a case study. Based on logging data, water injection profile test data, subwell data, and production performance data, among others, the flow zone index (FZI static) was proposed as the static evaluation parameter of the flow unit. The relationship between cumulative water injection (WT) and FZI change ( △ FZI ) was fitted. Hence, the △ FZI caused by water injection is combined with the static parameter of flow unit evaluation (FZI static) as the dynamic parameter of flow unit evaluation (FZI dynamic). The comprehensively evaluated reality of flow units in different periods is characterized by formula FZI static + △ FZI = FZI dynamic . The study shows that as the division standard of the flow unit, the FZI has a good correlation with the test results of the water absorption profile, such as water absorption intensity and relative water injection volume. Using the FZI as the static parameter of flow unit evaluation, four types of flow units were divided as follows: type I flow unit, FZI ≥ 4.1 ; type II flow unit, 4.1 > FZI ≥ 2.4 ; type III flow unit, 2.4 > FZI ≥ 1.7 ; type IV flow unit, 1.7 > FZI . The reservoir porosity and permeability characteristics of different flow units are highly correlated. Moreover, the relative permeability curve confirms that different flow units have different seepage capacities. Though, comparing characteristic reservoir parameters in different periods, the reservoir’s physical parameters became more conducive to fluid flow with the water injection development. The increase in the same water injection rate for type I and II flow units was greater than that for type III and IV flow units. Furthermore, when type I flow units were continuously distributed in a large area, high water consumption bands were formed, absorbing most of the water injection in the water injection wells. Hence, the waterflood efficiency was low. The change in different flow units was mainly controlled by the injection production well pattern and WT. Combined with the relative change characteristics of interlayer flow units, the changes can be divided into increasing type change and decreasing type changes. Finally, according to the distribution characteristics of different flow units, oil saturation, and water flooding results, strategies for tapping the potential of the remaining oil from three aspects (plane, interlayer, and inner layer) were formulated.

Identification and classification of water absorption profile of distributed optical fiber vibration signal based on XGBoost algorithm

Aiming at the problem that the layered water injection cannot be accurately obtained in the process of oilfield development, this paper proposes an optical fiber vibration signal recognition and classification algorithm based on XGBoost integrated learning. Firstly, the optical fiber vibration signal collected by the optical fiber vibration sensor is denoised by variational mode decomposition and reconstruction. Then generate spectrograms corresponding to different water absorption layers at different times. A dataset containing 3000 spectral images is obtained. The data sets are imported into support vector machine, random forest classifier and XGBoost integrated classifier based on decision tree for recognition and classification. The parameters of the obtained model are optimized and the model is evaluated by cross validation. Finally, the obtained models are compared and tested. The experimental results show that the XGBoost ensemble learning algorithm with decision tree as the base classifier can effectively identify different vibration signals. This method has a certain significance for the identification of layered relative water absorption of water injection profile.

Amylose Content and Physical Changes in Waxy Corn Starch Modification by Spontaneous Fermentation

This study aimed was to determine the changes in the ratio of amylose and amylopectin and the physical properties of spontaneously fermented waxy corn starch (WCS) granules. The results showed that the amylose content of WCS which was fermented spontaneously from 9 to 15 days experienced a significant change with native starch, namely, ± 86 – 117%. The hydrolyzed process is caused by lactic acid bacteria activity. The highest activity showed at 15th-day fermentation. Changes in starch composition also affect the swelling power, solubility, water absorption, and gelatinization profile of WCS. Starch that was fermented for 15th-days had the highest amylose percentage (24.92%) the otherwise, had the lowest swelling value compared to native starch. The percent solubility of fermented starch increased with increasing the amount of amylose and on the 15th day of fermentation, the highest value was (65.56%). Water absorption increased until the 6th-day of fermentation and then decreased due to an increase in the amount of amylose. The gelatinization profiles of native starch and fermented modified starch were of the same type.

Evaluation of Functional Features of Lignocellulosic Particle Composites Containing Biopolymer Binders.

In this research, the assessment of the impact of natural biopolymer binders on selected mechanical and physical properties of lignocellulosic composites manufactured with different resination (12%, 15%, 20%). Different mechanical and physical properties were determined: modulus of rupture, modulus of elasticity, internal bonding strength, thickness swelling, water absorption, contact angle, and density profile. Moreover, thermal properties such as thermogravimetric analysis and differential scanning calorimetry were studied for the polymers. The results showed significant improvement of characterized features of the composites produced using biopolymers. However, the rise of the properties was visible when the binder content raised from 12% to 15%. Further increase of biopolymer binder did not imply a considerable change. The most promising biopolymer within the tested ones seems to be polycaprolactone (PCL).

The Effect of Particle Size on the Physical Characteristics and Drug-release Behavior of Mini-tablets

This study aimed to investigate the influence of particle size of the excipients on the behavior of mini-tablets in terms of physical characteristics and drug release profiles. Material and methods: All of the mini-tablets based on HPMC, PEG 6K and PEO 8M PVP produced high quality mini-tablets from both sieve fractions while 90F was very fragile. Results: Crushing strength values were the most pronounced difference between the mini-tablets from all formulations. The PEO 8M-based mini-tablets showed the highest values and deformation behavior instead of fracture. Water absorption and drug release profiles also showed intriguing and different results between the various formulations. Conclusion: The results suggested that even though different particle size has limited effect on the physical characteristic of the product, it may have a significant effect on its drug dissolution profile. HIGHLIGHTS The particle size of powders or granules can influence the physical properties and release profiles of tablets, particularly mini-tablets PEG 6K and PEO 8M mini-tablets from the larger sieve fraction variation absorbed less moisture and released drugs faster than their counterparts, whereas HPMC and PVP 90F mini-tablets from both sieve fractions exhibited a similar pattern in terms of moisture uptake and drug release profiles PEO 8M mini-tablets of both sieve fractions displayed almost linear release profiles with the highest crushing strength than the rest of the formulations GRAPHICAL ABSTRACT

Application analysis of isotope water absorption profile in ternary test of second class weak alkali

In the weak alkali ASP flooding test of Pu II 4 - 9 reservoir in the second area of north east block of lamadian oilfield, the original well pattern of strong alkali ASP test area was used for backward development of Pu II 4 ~ 9 reservoir. According to the analysis of isotope water absorption profile results, the production degree of blank water flooding reservoir was obviously higher than that of strong alkali ASP test at the same stage. In this paper, the principle of isotope water absorption profile reflecting the utilization degree is analyzed, and it is considered that poor water quality is the reason for the large difference of utilization degree in test areas, and the feasible methods to reduce this kind of influence are put forward, and the corrected utilization degree in test areas is given.

A Prediction Model for Water Absorption Profile Based on IDW-DTW-RNN Method

At present, many low-permeability oil fields are entering the later stages of development, and there will be problems of difficulty in water injection and poor water injection effects. Obtaining water absorption profiles and their changes can more effectively help formulate layered water injection strategies. Generally, the isotope water absorption profile method is often used to obtain the water absorption profile. This method is accurate, but the test cost is higher and the actual oil field measurement data is less. Based on the measured water absorption profile data, this paper selects 8 factors including effective thickness of oil layer, effective permeability, measure coefficient, crude oil viscosity, crude oil volume coefficient, injection-production pressure difference, well spacing, and connection coefficient between oil and water wells as the main influencing factors of the profile prediction model. Taking water injection wells data with 8 factors as input, a water injection profile prediction neural network model based on inverse distance weighting method and dynamic time warping, namely called IDW-DTW-RNN, is trained in this study. This model is applied in oil field, and the accuracy is obviously improved compared with the conventional method, which is in line with the actual development situation. It provides a scientific basis for the adjustment and optimization of the later injection-production structure of the oilfield.

Synthesis of new PPG and study of heterogeneous combination flooding systems

For the problem wherein a reservoir demonstrates strong heterogeneity after polymer flooding and the conventional oil displacement method cannot effectively displace the oil in the low-permeability layer, preformed particle gel (PPG) is synthesized and forms a heterogeneous composite oil displacement system with a weak-base alkali–surfactant–polymer (ASP) system. The core flow and oil displacement experiments were conducted to test the PPG performance. The injection parameters of the heterogeneous system were optimized, and the oil displacement effect was evaluated. Results show that the best synthesis parameters of PPG are as follows – 25% acrylamide, 25% degree of hydrolysis, 1.5 × 10–3 g of cross-linking agent, and 2.25 × 10–2 g of initiator. PPG can swell slowly and has good salt and temperature resistance; the particles with different particle sizes have good elasticity and strength after complete expansion, and they have good compatibility with cores having different permeability values. Compared with the weak-base ASP system, the heterogeneous system can maintain interfacial tension on the order of 10–3mN/m when the concentrations of the alkali and the surfactant are low. The heterogeneous system can (i) achieve adaptive sealing of the formation owing to its good deformation recovery ability, (ii) play the role of liquid flow steering, (iii) adjust the water absorption profile, and (iv) improve heterogeneity. The optimal component concentration of the heterogeneous system is 500 mg/L PPG, 1400 mg/L polymer, 0.3% petroleum sulfonate, and 1.2% sodium carbonate, the best injection method being one wherein a heterogeneous system and a weak-base ASP system are injected alternately.

Research and Application of Optimized Integrated Profile Control in Wang 36 Well Area of Wangjiawan Oilfield

Aiming at the problems of serious heterogeneity of reservoirs in Wang 36 well area of Wangjiawan Oilfield, raPId rise of water cut in the oilfield, poor waterflooding development effect and unsatisfactory effects of conventional single profile control measures. Based on PI decision-making, a comprehensive profile-adjustment decision-making technique based on factors such as heterogeneity of water absorption profile and rising rate of water cut is developed. Field application shows that the overall profile adjustment of the block effectively improves the water flooding effect of Wang 36 block. This method has the characteristics of fastness, practicality and strong operability, and has important guiding significance for comprehensive treatment of similar oilfields.

Predictive model for water absorption in sublayers using a machine learning method

The sedimentary rhythm of Chinese oilfields is complicated and the heterogeneity is extremely strong. Allocating water absorption of each sublayer by dividing coefficient or numeric simulation cannot accurately reflect the actual water injection of the reservoir. Calculation based on water absorption profile monitored on site is the most commonly used method in oil field. However, access to these type of data is limited due to its cost and time related to acquisition. In this study, a machine learning approach was adopted to predict water absorption in sublayer based on geologic and production parameters of injectors and producers. On the one hand, it can save test costs. On the other hand, it can continuously predict water absorption of sublayers, and make up for water injection wells with insufficient injection profiles. A handful of training observations are obtained from on-site monitoring. Interwell connectivity is first conducted to identify connected producers for injectors. Introducing interwell connectivity helps to constitute predictor variables and yield significant improvements in feature selection. Connectivities in the well group are represented by similarity between injection sequence and production sequence, which is computed by Dynamic Time Warping. Average importance of predictors are then measured based on Mean Decrease Impurity, Mean Decrease Accuracy, and Ridge regression. Some relative important features are selected to consist the final predictors. The Extreme Gradient Boosting model is developed and then trained for making predictions given any set of observations. The proposed approach is validated by using actual field case from SL oilfield, China. Results show a significant correlation between predictions and actual value from on-site monitoring.

Research on heterogeneous compound flooding system based on dispersed particle gel

Aiming at the problem that the heterogeneity of the reservoir became strong, the remaining oil distributed universally after polymer flooding and the existing chemical compound flooding systems had limited application, a heterogeneous compound flooding system based on gel dispersion particles (DPG) was proposed as a substitution technology for further enhanced recovery of reservoirs after polymer flooding. This paper has carried out the design and characterization of heterogeneous compound flooding system, influencing factors, and application performance. With the system viscosity and oil-water interfacial tension as evaluation indicators, the application performance of the optimized heterogeneous polymer flooding system based on DPG was examined. The results showed that the system viscosity was 12.1 to 17.3 mPa•s while the interfacial tension was maintained at 10 -3 mN/m magnitude. At 80 °C, with 60 days aging, the viscosity retention ratio of the system is over 83.5%, and the interfacial tension between oil and water was still maintained at 10 -3 mN/m. The core flow experiment shows that, the heterogeneous compound flooding system has good injection performance, moving characteristics of plugging, breakthrough migration and re-plugging. After high-temperature aging, subsequent water flooding still maintained at a high pressure with good resistance to erosion. Through the selective high and low permeability layers, the water absorption profile was improved, and finally enhanced oil recovery to 20.61% after polymer flooding. Cited as : Li, H., Wang, K., Han, X., Zheng, J. Research on heterogeneous compound flooding system based on dispersed particle gel. Advances in Geo-Energy Research, 2019, 3(2): 156-164, doi: 10.26804/ager.2019.02.05