Ineffective Circulation Research Articles

Displacement Mechanism and Flow Characteristics of Polymer Particle Dispersion System Based on Capillary Bundle Model

During the development of oil reservoirs, a rapid increase in water cut following reservoir flooding leads to inefficient or ineffective circulation of injected water, rendering a significant portion of the remaining oil in the reservoir inaccessible. The displacement method using polymer particle dispersion systems effectively solves the issue of rapid water breakthrough in oil reservoirs. Owing to the particle phase separation phenomenon, polymer particles can selectively penetrate into the larger pores where water circulation is inefficient, enhance their flow resistance, and thereby achieve equilibrium displacement along with an increased swept volume. This paper investigates the heterogeneous distribution of polymer particles within a porous medium, incorporates the red blood cell dendrite concentration distribution theory from biological fluid mechanics, and develops a mathematical model to delineate the viscosity characteristics of polymer particle dispersion systems, taking into account the phase separation phenomenon. Building on this foundation, it formulates a capillary bundle model for the polymer particle dispersion system specifically designed for oil displacement and proceeds to determine its relative permeability curve. Simulation outcomes reveal that at a water saturation level of 0.063, the concentration of polymer particles in fractured large pore capillaries is markedly elevated, yet capillaries with a pore size under 26 μm remain devoid of polymer particles. With the increase of water saturation, the concentration of polymer particles in large pore capillaries reduces, whereas it progressively augments in medium pore capillaries. Upon reaching a peak water saturation of 0.751, capillaries smaller than 18 μm are entirely free of polymer particles. These findings suggest that the heterogeneous distribution of polymer particles markedly inhibits the percolation capabilities of the dispersed system following a water phase breakthrough, facilitating the entry of more dispersion into oil-laden capillaries and thus enhancing the flow capacity of the oil phase.

The Mechanism Study of Fracture Porosity in High-Water-Cut Reservoirs

Many onshore oil fields currently adopt water flooding as a means to supplement reservoir energy. However, due to reservoir heterogeneity, significant differences in permeability exist not only between different reservoirs but also within the same reservoir across different planar orientations. After prolonged fluid flushing in the near-wellbore zone of injection wells, the resulting increased flow resistance between layers exacerbates inefficient and ineffective circulation. A considerable amount of remaining oil is left unexploited in untouched areas, significantly impacting the overall recovery. To investigate the multiscale plugging mechanisms of fracture-dominated pore channels in high-water-cut oil reservoirs and achieve efficient management of fractured large channels, this study explores the formation of the fracture-flushing zone-low saturation oil zone. A physical experimental model with fractures and high-intensity flushing is established to analyze changes in pore structure, mineral composition, residual oil distribution, and other characteristics at different positions near the fractures. The research aims to clarify the mechanism behind the formation of large channels with fracture structures. The results indicate that under high-intensity water flushing, cementing materials are washed away by the flowing water, clay particles are carried to the surface with the injected fluid, and permeability significantly increases, forming high-permeability zones with fracture structures. In the rock interior away from the fracture end, channels, corners, and clustered oil content noticeably decrease, while the content of film-like oil substantially increases, and clay minerals are not significantly washed away. Under strong flushing conditions, the number of residual clay particles near the fracture end is mainly influenced by flow velocity and flushing time; thus, the greater the flushing intensity, the faster the water flow, and the longer the flushing time, the fewer residual clay particles near the fracture end.

Experimental Study on Improving Oil Recovery Mechanism of Injection–Production Coupling in Complex Fault-Block Reservoirs

In order to improve the effect of injection–production coupling development to improve crude oil recovery in complex fault-block reservoirs, we carried out a physical simulation experiment based on a sandpack model of transforming water-driven development into injection–production coupling development and quantitatively evaluated the influence of rounds of injection pressure coupling on the crude oil mobilization in reservoirs with different permeability levels and on oil recovery. Meanwhile, the characteristics of residual oil were studied via a numerical simulation method. The mechanism of increased oil production via injection–production coupling development was revealed by analyzing the water and oil contents, formation pressure, and streamline fields through the establishment of mechanism models. The results of the physical experiment show that injection–production coupling can improve the recovery effect of medium- and low-permeability reservoirs by 55.66%. With an increase in the injection pressure, the oil recovery percentage of the low-permeability sandpack model at 20 MPa is 100%, and this study finds that injection–production coupling is the main way to develop the recoverable oil in a low-permeability reservoir. The numerical simulation results show that among the four remaining oil distribution types (interwell-enriched, low-permeability zone-enriched, well network imperfection, and mismatch between injection and production), the interwell-enriched type of the remaining oil reserves accounts for the highest proportion (48.52%). The simulation results of the mechanism model show that water-driven development easily leads to streamline solidification, resulting in ineffective circulation of the injected water. Compared with conventional water-driven development, the pressure propagation range is significantly increased in injection–production coupling development. The reservoir streamline distribution is more continuous and uniform, and the flooding wave is wider in volume and range. This research provides a theoretical basis for the injection–production coupling technology policy in complex fault-block reservoirs.

Recent advances in mRNA-based vaccine for cancer therapy; bench to bedside.

The messenger RNA(mRNA) vaccines have progressed from a theoretical concept to a clinical reality over the last few decades. Compared to conventional vaccination methods, these vaccines have a number of benefits, such as substantial potency, rapid growth, inexpensive production, and safe administration. Nevertheless, their usefulness was restricted up to now due to worries about the erratic and ineffective circulation of mRNA in vivo. Thankfully, these worries have largely been allayed by recent technological developments, which have led to the creation of multiple mRNA vaccination platforms for cancer and viral infections. The mRNA vaccines have been demonstrated as a powerful alternative to traditional conventional vaccines because of their high potency, safetyand efficacy, capacity for rapid clinical development, and potential for rapid, low-cost manufacturing. The paper will examine the present status of mRNA vaccine technology and suggest future paths for the advancement and application of this exciting vaccine platform as a common therapeutic choice.

Study on the limit of ineffective cycle control in Lamadian Oilfield in the late period of ultra-high water cut

The ineffective circulation in Lamadian oilfield is mainly banded ineffective circulation and dendritic ineffective circulation, and the ratio of ineffective circulation to the total well production is mostly concentrated below 40%. Therefore, this paper first divides the levels of ineffective circulation and simulates the proportion of liquid production in different levels of ineffective circulation to get the limits of ineffective circulation management. The results showed that the invalidation index R < 0.2 was a fourth-grade invalidation cycle, 0.2≤R < 0.3 was a third-grade invalidation cycle, 0.3≤R < 0.4 was a second-grade invalidation cycle, and R≥0.4 was a first-grade invalidation cycle. The reduction of water injection in the planar heterogeneous layer will lead to the decrease of cumulative oil production, and the discrimination index R is small, and the reduction range is almost unchanged. When the discriminant index R is above 0.4, the reduction of cumulative oil production increases significantly.

Optimization of Gel Flooding during the High Water Cut Stage in a Conglomerate Reservoir of the Xinjiang A Oilfield.

Influenced by water injection, a dominant flow channel is easily formed in the high water cut stage of a conglomerate reservoir, resulting in the inefficient or ineffective circulation of the injected water. With gel flooding as one of the effective development methods to solve the above problems, its parameter optimization determines its final development effect, which still faces great challenges. A new optimization method for gel flooding is proposed in this paper. Firstly, the gel flooding parameters were obtained through physical experiments; then, an experimental model of gel flooding was established according to the target reservoir, and parameter sensitivity analysis was carried out. Next, a history matching of the gel flooding experiment was carried out. Finally, history matching of the target reservoir was also carried out, and a gel flooding scheme was designed and optimized to determine the best parameters. The experimental results showed that the gelation time was 4 h and the gel viscosity was 6332 mPa·s; the breakthrough pressure, resistance factor (RF), and residual resistance factor (RRF) all decreased with the increase in permeability. The gel had a good profile control ability and improved oil recovery by 16.40%. The numerical simulation results illustrated that the porosity of the high permeability layer (HPL) had the greatest impact on the cumulative oil production (COP) of the HPL, and the maximum polymer adsorption value of the HPL had the largest influence on the COP of the low permeability layer (LPL) and the water cut of both layers. Benefiting from parameter sensitivity analysis, history matching of the gel flooding experiment and a conglomerate reservoir in the Xinjiang A Oilfield with less time consumed and good quality was obtained. The optimization results of gel flooding during the high water cut stage in a conglomerate reservoir of the Xinjiang A Oilfield were as follows: the gel injection volume, injection rate, and polymer concentration were 2000 m3, 50 m3/d, and 2500 mg/L, respectively. It was predicted that the water cut would decrease by 6.90% and the oil recovery would increase by 2.44% in two years. This paper not only provides a more scientific and efficient optimization method for gel flooding in conglomerate reservoirs but also has important significance for improving the oil recovery of conglomerate reservoirs.

Research and Application of a Controllable Permeability Refracturing Technology in a High-Water-Cut Potential Layer

Summary The Fuyu oil field is a typical shallow, low-temperature, low-permeability reservoir. At present, the oilfield composite water cut is 95%, artificial fractures interlace with natural fractures, and the distribution of ineffective circulation channels between wells is complex. This paper found that after reducing the permeability of the original fracture, refracturing can effectively improve the longitudinal extension range of the new fracture through numerical simulation. Therefore, a controllable permeability temporary plugging agent is studied, and controllable permeability refracture technology is proposed. The controllable permeability temporary plugging system is composed of elastic particles, quartz sand, and quick-soluble elastic enhancers, which are based on elastic particles that do not age, and long-term plugging can be achieved. Through physical experiments, 0.5–1-mm elastic particles with 70–140 mesh and 16–30 mesh quartz sand were used in different ratios (i.e., 5:5, 6:4, and 7:3). According to the closure pressure and the permeability of the fracturing layer, the ratio chart of elastic particles and quartz sand is established. The controllable permeability refracture technology can select the ratio of the quartz sand and elastic particles according to the closure pressure and the control requirements of the fracturing horizon permeability. Through field applications, we found that, compared with the conventional refracturing technology, the average daily fluid gain per well decreased from 5.0 to 3.9 tons, and the daily oil gain increased from 0.3 to 0.6 tons. The controllable permeability fracturing technology could reduce the permeability of the original fracture and improve the vertical production degree of the reservoir after refracturing. In addition, this method ensures that the original fracture has a certain conductivity and that the high-permeability layer reserves are not lost due to temporary plugging agents, thus expanding the planar sweep volume and effectively improving reservoir recovery. Nevertheless, the chart established is mainly suitable for shallow reservoirs, and the closure pressure is 3–15 MPa in this paper. Further testing and research are needed for deep reservoirs.

Performance Evaluation and Action Mechanism Analysis of a Controllable Release Nanocapsule Profile Control and Displacement Agent.

With the acceleration in oilfield developments, reservoir advantage channels have been gradually developed. This has led to ineffective circulation in the oilfield injection system and a significant decrease in production. The profile control and displacement technology of low-permeability and heterogeneous reservoirs are in urgent need of updating. In this paper, an intelligent profile control and displacement agent is proposed. The controlled release mechanism and profile control and displacement mechanism is clarified by physical simulation experiments. The profile control agent is a nanocapsule with environmental response and controlled release. The structure of the capsule is a core-shell structure, which is composed of an amphiphilic copolymer AP-g-PNIPAAM and Janus functional particles. The surface chemical stability of the micro/nanocapsule is analyzed by a potentiometric method. The study shows that a temperature at 45 °C causes a potential change in the micro/nanocapsule, indicating that the micro/nanocapsule has a slow release at this temperature. When the temperature is in the range of 40 to 45 °C, the absorbance greatly increases; therefore, it is considered that the capsule wall LCST is about 45 °C. Heating causes the surface contraction of the capsule wall to intensify, the micropores in the capsule wall to increase, the release amount to increase and the release rate per unit time to increase. The release time increases proportionally with the increase in capsule wall thickness. When the release time is the same, an alkaline or acidic environment can improve the release rate of the nanocapsule. The effect of profile control and flooding is evaluated through different differential core models. The research shows that the controlled release micro/nanocapsule has a good environmental response and the internal components can be effectively controlled by adjusting the temperature or pH value. This research has shown that the nanocapsules have good application prospects in low-permeability heterogeneous reservoirs.

Review of the Pathophysiologic and Clinical Aspects of Hypokalemia in Children and Young Adults: an Update.

This article examines the regulatory function of the skeletal muscle, renal, and adrenergic systems in potassium homeostasis. The pathophysiologic bases of hypokalemia, systematic approach for an early diagnosis, and therapeutic strategy to avert life-threatening complications are highlighted. By promoting skeletal muscle uptake, intense physical exercise (post), severe trauma, and several toxins produce profound hypokalemia. Hypovolemia due to renal and extra-renal fluid losses and ineffective circulation activate secondary aldosteronism causing urinary potassium wasting. In addition to hypokalemic alkalosis, primary aldosteronism causes low-renin hypertension. Non-aldosterone mineralocorticoid activation leading to low-renin and low-aldosterone hypertension occurs in Liddle’s syndrome and apparent mineralocorticoid excess. Although there is enzymatic inhibition of cortisol synthesis in congenital adrenal hyperplasia, precursors of aldosterone produce low-renin hypokalemic hypertension. In addition to the glucocorticoid effect, hypercortisolism activates mineralocorticoid receptors in Cushing’s syndrome. Genetic mutations involving furosemide-sensitive Na+-K+-2Cl− co-transporters and thiazide-sensitive Na+-Cl− transporters result in (non-hypertensive) salt-wasting nephropathy. Proximal and distal renal tubular acidosis is associated with hypokalemia. Eating disorders causing hypokalemia include bulimia, laxative abuse, and diuretic misuse. Low urinary potassium (<15 mmol/day) and/or low urinary chloride (<20 mol/L) suggest a gastrointestinal pathology. Co-morbidity of hypokalemia with chronic pulmonary and cardiovascular diseases may increase the fatality rate.

The ternary combination of polymer gel, microsphere and surfactant for conformance control and oil displacement to improve oil recovery in strong heterogeneous reservoir

The reservoir heterogeneity of Suizhong 36-1 oilfield is very obvious, the average permeability reaches 2000mD. Long-term water injection development leads to serious water channeling in high permeability layers, resulting in ineffective circulation of injected water and reduction of oil recovery. It is urgent to form an effective EOR method. In this paper, the oil displacement effect of different combination slugs including polymer gel, polymer microsphere and surfactant is evaluated by means of conformance control and chemical flooding. Three-layer heterogeneous 3-D plate model is used for oil displacement experiment. The experimental results show that the combination slug sequentially composed of polymer gel, polymer microspheres and surfactant have the best oil displacement effect with the oil recovery increment by 21.2% after the first water flooding. In addition, using the best slug combination for two rounds flooding, the recovery factor increased by 28.2% compared with the first water flooding. This paper provides some new insights for enhanced oil recovery in strong heterogeneity reservoir.

Study on potential and distribution of remaining oil after polymer flooding in XX Oilfield

XX oilfield has been put into polymer flooding development for 24 years, with cumulative oil production reaching XX million tons. Since 2005, the first-class reservoirs of early polymer flooding have been transferred to subsequent water flooding. After long-term water flooding, polymer flooding and subsequent water flooding, these reservoirs are in the development stage of “double extra high”, with high reservoir production degree, serious ineffective circulation and highly dispersed remaining oil, which makes it difficult to further tap potential. Therefore, the remaining oil potential and distribution law are studied in the first class oil layer in XX area of oilfield, which provides geological basis for further development and adjustment of EOR.

Research on profile inversion controlling methods of multi-slug polymer alternative injection

ABSTRACTThe development practice of polymer flooding shows that the injection profile easily inverses during the process of single slug polymer flooding. The low effective or ineffective circulation of abundant injecting water in high permeability layer, low producing degree of low permeability layer and large polymer volume have influenced the sweep efficiency and oil recovery of polymer flooding. In view of these questions, the alternative injection method of various viscosity polymer slugs is studied. This paper explains the theory of enhanced oil recovery of multi-slug polymer alternative injection. The experiment results show that the alternative injection of high and low viscosity polymer slugs has a better effect than single slug polymer flooding. The mobility differences between high-low permeability layers can be effectively reduced. For a multi-layer heterogeneous reservoir, there is an optimal alternative cycle. Reasonable slug size can not only inhibit dominant channel forming in high permeability layer but also can effectively produce low permeability layer and control profile inversion to a certain extent. This provides a technical support for studying the controlling methods of profile inversion.

Application of research based on fine geology in oilfield development

As the oilfield development enters a high water-bearing stage, the water content of the main oil layer gradually increases, the inefficient and ineffective circulation is serious, and the remaining oil distribution is scattered. It is difficult to select the well and reservoir. Through comprehensive development of high-density 3D seismic work, the study area further elaborates the sedimentary microfacies of the reservoir, making the development of the reservoir and the connectivity between the oil and water wells clearer. At the same time, applying the well-seismic combination technology to the fault Understanding, further clarifying the relationship between injection and production, the understanding of the underground situation is becoming more and more clear. Based on the comparison and application of the fine geological research results in the study area, this paper expounds the role of fine geological research results in the remaining oil potential tapping in the extra high water cut period.

Research on Deep Profile Control Technology of Water Flooding in Lamadian Oilfield

After Daqing Lamadian Oilfield entered the stage of development of ultra-high water cut, the ineffective circulation of various oil layers was serious, which restricted the development benefit of oilfields. To this end, the research on deep profile control of water flooding is carried out, and the combination of polymer microsphere flexible diverting agent and bulk expanded particle slug is used to exert a slower blocking speed of polymer microspheres, and a certain resistance is established in the deep pores of the reservoir. To provide the main slug with aggregating residence time; to exert the superior advantage of flexible steering agent deformation and adhesion ability, to form a dynamic path-distributing mechanism in the deep cavity of the reservoir; to play the advantage of faster blocking speed of the bulk-expanding particles, to prevent the main section The plug was flushed by subsequent water injection. Through the multi-segment combination indoor core experiment, it is shown that the front section is filled with microspheres, the main section is filled with flexible agent, and the post-segment is filled with expanded particles, which can well block the invalid circulation part, improve the displacement effect and improve The recovery rate can reach 3.12 percentage points. On October 16, 2013, Daqing Lamadian Oilfield carried out a deep liquid flow steering test study on the 9-injection and 16-hole water-flooding group. The comprehensive water content of the affected oil wells decreased by 7.8 percentage points, and the cumulative oil increase was 5,435 tons. The rate is 2.7 percentage points, and the input-output ratio is 1:4.0, which has achieved better mine results.

Research on Identification Method of the Inefficient and Ineffective Circulation Well Layer in Tracer Flow Simulation

The development of old Daqing Oilfield has entered the late stage of extra-high water cut, and the situation of inefficient and ineffective circulation is serious. Based only on the static and dynamic geological parameters, it is far from satisfying the requirement of analysis and judgement in the case of that the current well pattern, well spacing and dynamic state have all changed greatly, so the difficulty of development and adjustment is increasing. In this paper, tracer numerical simulation method is used to quantitatively study the directional injection-production rate of injection-production well layers, and the chart of the relationship between liquid production and water cut under different oil prices is established. The benefit types of production layers in production wells are classified and quantitatively evaluated, and then the inefficient and ineffective layers of production wells and their main inflow direction are accurately identified, which provides a basis for water control and efficiency improvement of inefficient and ineffective circulation well layers.

Evaluation Method of Reservoir Producing Status Based on Cumulative Distribution Curve of Oil Displacement Efficiency

This paper provides a method for evaluating the status of old oilfield development. This method mainly uses the abundant coring well data of the oilfield to obtain the cumulative distribution curve of the displacement efficiency after the displacement efficiency of the statistical wells in the study area in a similar period is ordered from small to large. Based on the cumulative distribution curve of displacement efficiency, combined with the reservoir ineffective circulation limit, the cumulative water absorption ratio of reservoirs and other data are used to study the reservoir producing degree, calculate the degree of oil recovery, evaluate the proportion of the remaining movable oil after water flooding, calculate the reservoir ineffective circulation thickness and ineffective circulation water volume, and so on.

Response to Fluid Boluses in the Fluid and Catheter Treatment Trial

Recent emphasis has been placed on methods to predict fluid responsiveness, but the usefulness of using fluid boluses to increase cardiac index in critically ill patients with ineffective circulation or oliguria remains unclear. This retrospective analysis investigated hemodynamic responses of critically ill patients in the ARDS Network Fluid and Catheter Treatment Trial (FACTT) who were given protocol-based fluid boluses. Fluid responsiveness was defined as ≥ 15% increase in cardiac index after a 15 mL/kg fluid bolus. A convenience sample of 127 critically ill patients enrolled in FACTT was analyzed for physiologic responses to 569 protocolized crystalloid or albumin boluses given for shock, low urine output (UOP), or low pulmonary artery occlusion pressure (PAOP). There were significant increases in mean central venous pressure (9.9 ± 4.5 to 11.1 ± 4.8 mm Hg, P < .0001) and mean PAOP (11.6 ± 3.6 to 13.3 ± 4.3 mm Hg, P < .0001) following fluid boluses. However, there were no significant changes in UOP, and there were clinically small changes in heart rate, mean arterial pressure, and cardiac index. Only 23% of fluid boluses led to a ≥ 15% change in cardiac index. There was no significant difference in the frequency of fluid responsiveness between boluses given for shock or oliguria vs boluses given only for low PAOP (24.0% vs 21.8%, P = .59). There were no significant differences in 90-day survival, need for hemodialysis, or return to unassisted breathing between patients defined as fluid responders and fluid nonresponders. In this cohort of critically ill patients with ARDS who were previously resuscitated, the rate of fluid responsiveness was low, and fluid boluses only led to small hemodynamic changes.

Investigation on Circulating Path of Injected Water for High Water-Cut Oilfield

In this paper, the indexes have been determined for identifying ineffective injection-production circulation and corresponding mathematical model was constructed with fuzzy theory. Application examples show that this method is simple, fast and accurate. For high and extra-high water cut oilfields, because of the long-term erosion of injected water, there are some high penetrative channels between the injection and production wells, resulting in most injected water along the channel to cause the invalid injection and production, for which it is hard to increase water flooding swept volume, causing flooding and high water cut well and reducing oil production. To improve the effectiveness of water injection to achieve stable yields, it is important to take the measures of ineffective injection-production wells profile control, plugging and so on for fast and accurate identifying ineffective injection-production wells. To that end, this paper applied fuzzy theory to establishing the mathematical model for identifying ineffective injection-production wells.

Study on the Fine Optimization of Water Injection in SZ Oilfield of Bohai Bay

Bohai SZ Oilfield has entered into high water cut stage, how to realize the goal of fine optimization of water injection to enhance oil recovery is an important problem for reservoir engineers. Fine optimization of water injection needs ‘inject enough’, ‘inject well’ and ‘inject effectively’. The paper gets relationship between annual oil production rate and annual water production rate of different water cut stages of SZ Oilfield with the life cycle theory and draws the annual water injection rate and annual oil production rate chart to ensure ‘inject enough’, optimizes injection allocation method according to new reservoir research and gets a very good precipitation effect of increasing oil production. The paper also puts forward the method to recognize low effective and ineffective injection circulation to guide the oilfield ‘inject effectively’. Key words : Fine optimization of water injection; Logistic theory; Prediction of water injection; Injection allocation; Low effective and ineffective injection circulation

The Research on Improving the Efficiency of Injection-Production of the Lamadian Oilfield in Ultra-High Water Cut Stage

With the oil field developing, the water cut increased, gradually and the efficiency of injection-production reduced year by year. Since the water flooding of Lamadian Oilfield entered extra high water cut period, the distribution of flow flied become more and more complex. The distribution of remaining oil and ineffective circulation is complex. The existing of ineffective circulation led to the flooding efficiency reducing sharply and cost of crude oil per ton by water flooding increased. In order to control production energy consumption in the extra high water cut, the method of improving the efficiency of Injection-production is studied in the Lamadian oilfield. Through the analysis of injection-production status, the factors that influence the injection efficiency is studied. The distribution of ineffective circulation which seriously affects the efficiency of Injection-production is made clearly. According to the factors that influence the efficiency of injection-production, based on flow field characteristics of water flooding, the countermeasure to enhance efficiency of injection-production is put forward in order to reduce the energy consumption and cost of producing crude oil.