Polymer Plug Research Articles

Investigation of the Effect of Residual Oil and Wettability on Sulfonated Polymer Retention in Carbonate under High-Salinity Conditions

Summary Polymer flooding in carbonate reservoirs is greatly affected by polymer retention, which is mainly due to adsorption by polymer-rock surface interactions. Consequently, this leads to a delay in polymer front propagation and related oil recovery response. This work investigates the effects of residual oil (Sor) and wettability on sulfonated-based (ATBS) polymer retention under the conditions of high salinity and moderate temperature. Polymer single- and two-phase dynamic adsorption tests as well as bulk and in-situ rheological experiments were conducted on outcrop carbonate cores in the presence of a high-salinity brine of 243,000 ppm at a temperature of 50°C. A total of four corefloods were conducted on Indiana limestone core samples with similar petrophysical properties. Overall, polymer adsorption was found to be low and within the acceptable range for application in carbonate reservoirs in the absence and presence of Sor. Furthermore, the polymer adsorption and in-situ rheology tests highlighted the significance of oil presence in the core samples, where retention was found to be around 40–50 µg/g-rock and 25–30 µg/g-rock in the absence and at Sor, respectively. An additional 50% reduction in retention was observed on the aged core sample that is more oil-wet. Polymer retention/adsorption was measured by double slug and mass balance techniques, and the results from both methods were in agreement with less than 7% difference. Inaccessible pore volume (IPV) was also calculated based on the double slug method and was found to be in the range of 23% to 28%, which was qualitatively supported by in-situ saturation monitoring obtained from an X-ray computed tomography (CT) scanner. The ATBS-based polymer showed excellent results for applications in carbonate without considerable polymer loss or plugging. This paper provides valuable insights into the impacts of residual oil and wettability on polymer adsorption, supported by CT in-situ saturation monitoring, which is necessary to avoid unrepresentative and inflated polymer retentions in oil reservoirs.

Development and Application of Polymer Plugging Remover for Polymer Injection Well in Changqing Oilfield

Water injection is a conventional method to maintain reservoirs pressure and improve production in low permeability oilfield. To decrease high water-cut and further enhance oil recovery, Polymers, such as polymer microsphere, preformed polymer gel, cross-linked polyacrylamide, are extensively used to control injection profile in Changqing oilfield. However, due to the low permeability and narrow pore throats of tight reservoirs, pressure in some water flooding wells increases rapidly after the polymer was injected, negatively affecting the energy supplement of the well cluster. A polymer plugging remover, composed of oxidizer, acid and chelating agent to relieve blockage, was developed with viscosity reduction and structure decomposition. The release period is more than 48 hours, which is conducive to deep-seated plugging removal. After treatment, the average diameter of polymer residue is 39-254nm and the dissolution rate is 15.76-53.42%. The permeability of the core sample plugged with polymer has increased significantly before and after treatment by polymer plugging remover, especially, it recovered by 28.67% for microsphere polymer. Five field tests have been completed successfully in the Jiyuan oilfield of Changqing. Before treatment, conventional acidification was performed in the pilot wells for two times at least, which is proved invalid. However, after polymer degraded by the plugging remover, the injection rate increased by 16.2m3/d, the pressure dropped by 3.4MPa and the validity period has exceeded 130 days on average. The polymer plugging remover provides an alternative way to increase injectability when dealing with high pressure and under-injection wells caused by polymer flooding.

CO2 diffusive characteristics and influencing factors in the porous medium with saturated polyacrylamide solutions

Polyacrylamide has been widely utilized to store CO2 in reservoirs in order to alleviate the greenhouse impact. However, no studies have been conducted on the motion of CO2 in a polyacrylamide solution within porous media. This study illustrates the effect of polyacrylamide molecular weight, concentration, pressure, temperature, and pore size on the dynamic diffusion of CO2 in the core with saturated polyacrylamide solutions. The diffusion motion characteristics of CO2 were obtained by diffusion experiments. The microscopic analysis of core slices following testing showed the presence of polyacrylamide on rock particles. The pressure and CO2 mass fraction distribution inside the core were calculated by constructing a mathematical model. The results show that the increase in molecular weight and concentration of polyacrylamide decreased the diffusion ability of CO2, while temperature and pressure accelerated the diffusion of CO2. The polyacrylamide moved into the core to form an effective inhibiting effect, which was affected by CO2 and pressure. While the increase in pore size accelerates the flow rate of the polyacrylamide, it also enhances the sealing capacity of the polyacrylamide solution. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that the core had a high content of polyacrylamide solution inside it, and these molecules were attached to the surface of the core particles in an irregular lamellar pattern. The calculation model was consistent with the diffusion experimental results, where the CO2 diffusion coefficient in the polyacrylamide solution was in the order of 10-12 m2/s under the conditions of 5–30 MPa, 323–343 K, and a core permeability of 60 × 10-3 μm2. The results of this paper provide a new calculation for evaluating the performance of polymer plugging.

Experimental studies on the performance evaluation of water-soluble polymers used as temporary plugging agents

The performance of the temporary plug is a key factor in determining the success of loss-circulation control and temporary plug diversion fracturing. Due to the complexity of geomechanics and working conditions, current commonly used temporary plug agents face problems such as low plug strength and efficiency, large filtration losses due to failure to form filter cakes, and slow degradation affecting the recovery of fracture conductivity. A novel idea for the development of a novel water-soluble polymer plug for fracking is proposed, namely, low-to middle-molecule weight + reinforced chain rigidity + supramolecular aggregation. Using sodium bisulfite and potassium sulfate as initiators, AA, AM, and AMPS as grafting monomers, and SM as hydrophobic functional monomers, the AM-AA-AMPS-SM copolymer was prepared by polymerization. The developed new temporary plugging agent was completely degraded at 70°C for 5–8 h by carrying out experimental evaluation tests, such as water absorption expansion rate, swelling kinetics, density, post-dissolution viscosity, strength of the temporary plugging agent and post-degradation conductivity. After degradation, the viscosity of the solution is 2.5–3.6 mPa s with good fluidity and no gel remnants. The density of the temporary plug material is about 1.14 g/cm3. The absorption expansion rate was 25.8 g/g. The pressure is 60.1 MPa when the thickness of the granular temporary plug is 0.4 cm. Under experimental conditions, the fracture conductivity was found to be 69–123 D*cm at a closing pressure of 30 MPa after degradation of the temporary plug. The test results demonstrate that the new temporary plug agent, with its high plug strength, temperature-controlled degradation, reflux stability and effective self-support after degradation, can meet the requirements of drilling plug and temporary plug fracturing technologies.

Research Progress of Intelligent Polymer Plugging Materials

Intelligent polymers have become the focus of attention worldwide. Intelligent polymer materials through organic synthesis methods are used to make inanimate organic materials become "feeling" and "sentient". Intelligent polymer materials have been applied in actual engineering production, and they are becoming a new research topic for scientists in various fields and countries, especially in the areas of drilling and plugging. The development of intelligent polymer materials can provide new solutions and technical means for drilling and plugging. Unlike traditional plugging materials, intelligent polymer plugging materials can cope with environmental changes. They have the characteristics of a strong target, good plugging effect, and no damage to the reservoir. However, there are currently no reviews on intelligent polymer plugging materials in the drilling field, so this paper fills that gap by reviewing the research progress of intelligent polymer plugging materials. In addition, this paper describes the mechanism and application status of intelligent polymer shape-memory polymers, intelligent polymer gels, intelligent polymer membranes, and intelligent polymer bionic materials in drilling and plugging. It is also pointed out that some intelligent polymer plugging materials still have problems, such as insufficient toughness and a poor resistance to salt and high temperature. At the same time, some suggestions for future research directions are also presented for reference.

Effect of pressure-driven flow on electroosmotic flow and electrokinetic mass transport in microchannels

The coupling of pressure-driven flow (PDF) and electroosmotic flow (EOF) has been widely applied in the field of microfluidics. However, the adverse effects of pressure induced by PDF on EOF in a confined space cannot be ignored. Herein, the interactions of these two streams when the Reynolds number (Re) varies from 0.1 to 10 are systematically explored through numerical simulations to gain an in-depth understanding of the mechanism of the pressure effect on mass species transport and to generate optimal separation of samples. The simulation results show that the length of the sample increases linearly and the molecular diffusion is accelerated due to the pressure effect caused by the EOF channel structure and PDF extrusion, which reduces the separation quality and even leads to the failure of electrophoresis. However, the deformation of the sample cannot be effectively resisted by increasing the applied voltage. A better separation effect can be obtained only when Re=0.1. To surmount the above disadvantages, a novel porous polymer plug with pores smaller than 5 μm that provides a region that has high flow resistance but allows the electromigration of charged analytes is established in the EOF channel. The experimental results show that this plug can effectively neutralize the EOF outlet pressure when Re≤5. The shape of the sample is not distorted and the maximum gray values decreased by 26%, 30% and 49% respectively in 7 s when Re=0.1, 1 and 5, which are much better than the results without the plug.

Automotive Diesel Fuel Internal Stability Testing with the Use of UV and Temperature as Degradation Factors

Diesel fuel stability can be considered from many points of view, of which the two considered most important are stability in contact with the environment and internal stability. Fuel stability in touch with the environment is often defined as oxidation stability, of which measurement procedures are well developed. The presented paper shows that fuel's internal stability can also be important. The internal stability of diesel fuel with the local use of thermal and ultraviolet radiation (UV) as degradation factors and fluorescence signals as a probe is presented in this paper. We show that the internal degradation of fuel with temperature use differs from that with UV and simultaneous both factors use. Our study shows that using temperature as a degradation factor introduces significant fluorescence fading. Moreover, the fluorescence signal restores significantly later than the sample stabilizes at room temperature. The novelty proposed based on examination is hybrid degradation and an examination cycle that enables the simultaneous use of degradation factors and fluorescence reading. For this purpose, a dedicated measurement setup of signal control and processing was constructed and programmed. The measurement procedure of the data series for specific wavelength enables calculation of signal shifts that allow the internal stability classification of diesel fuel samples in less than 30 min with the cost of a single disposable capillary probe and one polymer plug. Premium and regular fuel examination results show that internal fuel stability can be related to polycyclic aromatic hydrocarbons (PAH) concentrations and can be modified with dedicated additives.

Dual-pulse Release System of Atenolol: Preparation and in-vitro Characterization

Abstract: Aim: Hypertension exhibits a circadian rhythm and drugs need to be released at the time when the blood pressure is elevated most. This elevation is pronounced at 7 pm and at 4 am. Atenolol is an anti-hypertensive drug with an absorption window mainly in the upper section of the gastrointestinal tract. The present investigation was aimed at designing floating pulsatile capsules for dual release of atenolol in the stomach for effective management of hypertension. Materials and Methods: The floating pulsatile capsules designed had different components: a formaldehyde-treated capsule body; an untreated cap; a polymer plug layer, containing a polymer; two atenolol-containing immediaterelease tablets and a swellable polymer layer. The polymer plug layer was made of hydroxypropyl methylcellulose (K4M or E50) and xanthan gum alone or in combination. The capsules were characterized for weight variation, percent drug content, in-vitro release behaviour and floating property. Results: The outcomes of the in-vitro studies showed that lag duration between the two pulses of drug release from the formulations can be adjusted by manipulating the composition of the plug layer. The optimized floating pulsatile capsule provided the first pulse of the drug immediately after administration to cover the first point of the symptoms. It provided the drug release from second pulse after a lag time of 8 hr for covering up the second point of the symptoms in the early morning. Conclusion: Thus, the dual-release floating pulsatile capsule designed may be used for chronological treatment of hypertension. Keywords: Hypertension, Pulsatile, Floating, Lag time, Capsule, Plug layer.

Gel-Forming and Plugging Performance Evaluation of Emulsion Polymer Crosslinking System in Fractured Carbonate Rock

The water channeling of fractured carbonate rock seriously affects oil recovery, and this problem is especially serious in the Kazakh North Troyes oilfield. A conventional powder polymer plugging system needs to be hydrated ahead of time, which increases the cost and difficulty of field operation and it cannot realize large-scale plugging operations. The new emulsion polymer crosslinked system can realize rapid hydration and real-time mixing, having low base liquid viscosity and good fluidity and injectability. The results of the laboratory study show that the gelling time of HR9806 emulsion polymer and organic chromium crosslinker was 6~8 h. 0.5 wt % HR9806, which is recommended for field use with P/C ranging from 2.5 to 5.0. The emulsion polymer crosslinking system was found to be highly adaptable in reservoirs and had salinity resistance. Mineral salt and reservoir core were able to enhance the gel strength of the system but shortened the gelling time of the system by about 2 h. The gel (HR9806) had good shear resistance. It still had a viscosity of 220 mPa·s under high-speed shearing (Temperature = 54 °C), and the formed gel system shear resistance increased with increasing concentration. The emulsion system of “0.50 wt % HR9806 emulsion polymer + 0.15 wt % organic chromium crosslinker + brine” had a strong plugging effect in the fractured core and sand-filled pipe model, with residual resistance coefficient ≥30, effective plugging rate ≥ 95.0%, and oil–water selectivity of 0.45. In this paper, the levels of weak gel strength were used, providing an experimental and theoretical reference for improving the application effect of the weak gel system in the field. The study found that the weak gel system can better enter the fractured carbonate reservoir and form a plugging effect in the fracture, improving the effect of subsequent water flooding matrix oil recovery.

Study on the Relationship between the Relative Molecular Mass of a Polymer Clay Stabilizer and the Permeability of a Tight Reservoir.

Water-sensitivity damage is inevitable during hydraulic fracturing for tight reservoir stimulation. A polymer clay stabilizer is the most effective and commonly used agent for reducing this kind of permeability damage. However, due to the small pore throat radii of tight reservoirs, polymers may be captured and detained, resulting in secondary permeability damage caused by polymer plugging. Therefore, it is necessary to clarify the matching relationship between the relative molecular mass of the clay stabilizer and the permeability of tight cores, which has not been reported yet. In response to this problem, the residual resistance factor and the permeability damage rate of PDMDAAC (poly dimethyl diallyl ammonium chloride, a kind of commonly used polymer clay stabilizer) to tight cores from Xinjiang Oilfield were investigated in cores with permeabilities of 0.10 × 10–3 μm2 (0.08–0.17 × 10–3 μm2), 0.05 × 10–3 μm2 (0.035–0.065 × 10–3 μm2), and 0.01 × 10–3 μm2 (0.007–0.020 × 10–3 μm2) through flow experiments. It was found that the relative molecular masses of PDMDAAC, which did not cause obvious core permeability damage, should be less than 10 000, 5000, and 2000, respectively. In addition, the bridging flocculation principle between the hydrodynamics radius of the clay stabilizer and the radius of the tight core pore throat can be used to explain the matching relationship between the relative molecular mass of the polymer clay stabilizer and the permeability of the tight reservoir. This study points out the direction for the optimization of the polymer clay stabilizer used in tight reservoir hydraulic fracturing and provides some references for the construction of hydraulic fracturing fluid systems for the efficient development of unconventional oil and gas resources.

Effects of water-based drilling fluid on properties of mud cake and wellbore stability

The challenge of wellbore stability is getting harder in complex formations. A better understanding of mud cake and its effect on stress state around the wellbore is beneficial for the solution of wellbore stability problems. Thus, the testing method and describing function of dynamic mud cake properties were developed with different drilling fluid additives. The microstructure of mud cake was investigated to further illustrate the mechanism of drilling fluid additives. Based on the poroelastic model, the effect of time-dependent mud cake properties on the distribution of pore pressure, effective stress state around the wellbore and safe mud weight window was analyzed. The results indicate that the buildup of mud cake slows down the increase of pore pressure and broadens the safe mud weight window by increasing the effective stress of compression. The significant increase in fracturing pressure illustrates the potential effect of mud cake in wellbore strengthening. Although the pressure isolation effect increases with the addition of bentonite, it has a limited influence on the safe mud weight window. The addition of Xanthan (XC) enhances the pressure isolation effect of mud cake by improving the coalescence stability of fine-grained particles and plugging the pore with hydration membrane. The viscoelastic granular plugging material has the best sealing efficiency with the deformation property. Although the fine-grained walnut shell has a relatively good pressure isolation effect, its effect on borehole cleaning is far greater than that on wellbore stability. • The testing method and descriptive function of dynamic mud cake properties were developed. • A hydro-mechanical model was developed with the effect of time-dependent mud cake. • The combination of bentonite, polymer and viscoelastic plugging material had the best pressure isolation effect. The addition of plugging material decreases the pore pressure, which indicates that the pressure isolation effect of mud cake can be effectively improved with the packing of rigid particles (Fig. 20). When the content of plugging material is high, the pore pressure decreases slightly, which illustrates that the increase of rigid materials cannot obviously enhance the compactness of the plugging zone. The addition of plugging material increases the effective stress of compression, which shows that the plugging of rigid particles decreases the risk of wellbore instability with higher compressive strength.

Pulsatile Delivery of Fexofenadine Hydrochloride Pulsincap by Box-Behnken Design

Objective: Fexofenadine hydrochloride is a selective peripheral H1-blocker, used for allergy symptoms, such as hay fever and urticaria. Allergic symptoms are aggressive during early morning hours, so a pulsatile delivery system with a lag time of 4-5 hours was formulated and optimized by Box-Behnken design.
 Materials and Methods: Pulsincap system using formaldehyde-treated capsules and hydrogel plug. Box-Behnken design was applied for optimization in which three independent variables, X1= Drug: polymer ratio, X2 = Polymer: polymer ratio (Ethylcellulose: HPMC E15) and X3 = Plug weight were selected. Three dependent variables R1 = Percent release of drug after 4 hours, R2 = percent release after 10 hours and R3 = Lag time were selected.
 Results: FTIR and DSC studies confirmed compatibility of drug and excipients. The empty formaldehyde-treated capsules were evaluated for physical appearance, solubility, capsule dimensions and formaldehyde content. Hydrogel plugs, powder blend and pulsincap formulations were evaluated for Physico-chemical parameters and all the parameters were within acceptable limits. Contour plots and Response surface plots indicated that as Drug: Polymer ratio (X1) and Plug weight (X3) increased, Lag time increased but% drug release decreased. As Polymer: Polymer ratio (X2) increased, the lag time was at a moderate level. Predicted vs actual responses showed the correlation of 0.786 for% release in 4hrs, 0.9744 for% release in 10hrs and 0.6281 for lag time. Optimized formulation G1 was suggested by design (with criteria 4.5-6hrs lag time, 10-20% release in 4hrs & 60-70% drug release within 10hrs). The optimised formulation was stable.
 Conclusion: Pulsincap system of Fexofenadine hydrochloride can be obtained by using retarding polymers like ethyl cellulose, HPMC E15 and formaldehyde cross-linked capsules.

Investigating the effects of polymer plugging mechanism of liquid production decrease and improvement by the cross-linked gel performance

Polymer flooding, as the most successful and well-known chemical EOR method was broadly applied around the world. Mostly, contrasted with Waterflooding, the production rate decrease during polymer flooding is smaller based on field application. Nevertheless, the production liquid rate decreased critically in the middle phase to late phase due to plugging, which could lead the way to poor flooding performance and fewer cumulative oil. In this work, first, we approached the affecting polymer plugging mechanism model on liquid production decrease to investigate the parameters such as; solid-phase concentration (SOLIDMIN), reacting frequency factor (FREQFAC) and others affecting components are all investigated consecutively. Secondly the model approached by cross-linked gel for the improvement of production liquid rate. The physical work was designed by a physical model, and then the polymer adsorption that generating blockage emerging in permeability diminish assessed by a mathematical model. The outcomes specify that the existence of this debris, excessive assemblage of solid-phase and the excessive reactant frequency factor has major mechanical and physical parameters effects on the reservoir throughout polymer flooding. Polymer flood model base case liquid ratio loss is 11.15 m3/day between the years 2014-08-01 to 2020-03-04. Comparing with the polymer flood model case 1, liquid ratio loss ranging to 1.97 m3/day between the years 2014-08-02 to 2020-03-03. While the oil ratio loss of the polymer flood base case model between the years 2015-07-08 to 2020-03-04 attained 12.4 m3/day contrasting with the polymer flood model case 1 oil ratio increase to 0.37 m3/day between the years 2014-08-04 to 2019-04-02. The cross-linked gel model base case liquid ratio loss is 2.09 m3/day between the years 2015-01-02 to 2020-02-03, while the oil ratio lost reached 9.15 m3/day between the years 2015-09-01 to 2020-02-03. Contrasting with the cross-linked gel model case 2 liquid ratio recovered from the loss and attained 25.43 m3/day in the year 2020-12-01, while the oil ratio is reached 15.22 m3/day in the year 2020-12-01. Polymer flood model examined through cross-linked gel model performed reliable outcomes by taking out the plugging, which also occasioned the reservoir production rate to decrease. With the application of cross-linked gel the affected parameters and the production rate have achieved an improvement.

Corrosion inhibitor system for blocking polymer well by potassium persulfate injection

Purpose This paper aims to clarify the corrosion inhibition effect of different corrosion inhibitor systems on the corrosion of metal pipe string by potassium persulfate plugging agent, so as to improve the injection capacity of polymer plugging well and reduce the corrosion of steel by oxidant plugging agent. Design/methodology/approach The effect of different corrosion inhibitors on the corrosion inhibition of N80 carbon steel in 1% potassium persulfate solution was studied by electrochemical experiment and weight loss experiment. The corrosion inhibition mechanism of potassium persulfate inhibitor and the synergistic mechanism among different inhibitors were analyzed. Findings The results indicated that when the temperature was 50°C, the inhibition effect of 0.2% sodium molybdate with a single inhibitor was the best at pH 8.5, and the inhibition rate was 70.17%. The inhibition efficiency of 0.2% sodium molybdate + 0.3% sodium silicate in the composite inhibition system can reach 94.38%. In the temperature range of 20°C–60°C, with the increase of system temperature, the inhibition effect of corrosion inhibitor will gradually weaken. Originality/value The corrosion inhibition system of N80 steel in potassium persulfate oxidant was mainly studied, and it clarified the influence of temperature and pH value on the corrosion inhibition effect, which provided guidance and suggestions for the corrosion inhibition of tubular string in the oilfield.

Advanced Well Control Reduces Risk of a Blowout

AbstractThere are still concerns about well control especially for operations in sensitive environments. Currently the final barrier while drilling oil and gas wells is a valve system (blowout preventer or BOP) located on top of wells. These valves can isolate wells by sealing around or shearing through obstructions in the well (e.g. drilling pipe and casing). If these valves fail or if some other barrier in a well fails, hydrocarbon loss to the environment is possible. Adding barriers capable of responding to a well control loss could alleviate these concerns. ExxonMobil is currently evaluating concepts to provide two additional methods to kill an out-of-control well. One utilizes rapid crosslinking polymers to form a polymer-plug seal inside a BOP after a failure. The other is to rapidly pump seawater into a well to produce back pressure that overpressures the entire well bore to keep hydrocarbons from escaping oil / gas bearing zones.Mixing dicyclopentadiene (DCPD) and other monomers with a ruthenium-based catalyst causes a rapid polymerization reaction that forms a high-strength, stable solid. These reactions can occur under extreme temperatures and pressures while withstanding significant contamination from other fluids and solids. The well-control concept is to rapidly pump the monomers and catalyst into a leaking BOP to form a polymer seal that prevents further flow.The seawater injection concept uses high-pressure and capacity pumps located on a surface vessel and a conduit from these pumps to a port on a BOP. If a blowout occurs, seawater at high rate is pumped in the BOP. If BOP seal failure is the reason for containment loss, then the seawater will overpressure the BOP and seawater will displace the hydrocarbons passing through the leak point. Seawater injection will also overpressure the entire wellbore to keep hydrocarbons from escaping anywhere in the well. For example, if a leak occurs deep in the well, seawater injection into the BOP will overpressure the entire well and the seawater will replace the hydrocarbon flowing through the leak point.We have conducted testing of the polymer plug concept at representative temperatures and pressures using a small-scale BOP. Polymer seals were formed when the scale BOP was flowing drilling mud, a crude-oil surrogate, and water. The seals held up to 5,000 psi pressure for almost 18 hours. We have completed modeling of the seawater injection concept to define pumping needs. This paper describes the current status of concept development.

Research and application of pressure decreasing technology of polymer material injection wells

Injecting polymer materials is an important means to improve the ultimate recovery, maintain stable production and improve the development effect of the oil field in the high water cut period. However, in the development process of polymer flooding, with the continuous increase of the cumulative polymer injection, the problem of high-pressure under-injection frequently occurs in the injection well. In this paper, based on geological characteristics and plugging material analysis, the causes of high pressure/under-injection and production characteristics of different types of measure wells. To study and optimize the rubber breaking, degradation and synergistic acidification liquid system that are applicable to different blockage conditions can effectively improve the adaptability of the blockage liquid system; Meanwhile, the formation of a quick plugging process with the characteristic of “single-stage single-step injection + prescription formula structure” can effectively improve the success rate of polymer plugging process measures, providing strong technical support for polymer flooding technology.

Securing Annulus Abnormal Pressure Build-up (APB) with Polymer Plug; a Case Study

The life cycle of a production well was facing challenges related to well integrity issue where A-Annulus pressure tracking the tubing pressure and increased repeatedly above the Maximum Allowable Wellhead Operating Pressure (MAWOP). Several well control operations were executed to reduce A-Annulus abnormal pressure build-up (APB) with no success.Literature and well historical studies were performed in order to secure this well, normal bleed and lube was ruled out owing to several attempts already performed for more than a year, but the APB keep on appearing after 2-4 months. Bullheading is not a viable option to kill the well. Well securing planned and prepared with some options such as, mechanical barriers/plugs, cement plug or polymer plugs as temporary plug to avoid APB re-occurrence. There were some constrains in operation planning that need to be addressed carefully, with additional challenge of tight injectivity as if it was a closed system.The polymer plug successfully stops the gas migration to surface, and secured the well from any reoccurrences of APB. The details of well control histories, operation design and planning and operation execution with the complete results and evaluation will be presented in this paper.

Recanalisation of a Superficial Temporal Artery Pseudoaneurysm after Vascular Plug Embolisation

A 32 year old man, treated four years previously for a post-traumatic superficial temporal artery (STA) pseudoaneurysm, presented with pulsatile tinnitus. (A) Computed tomography angiography revealed a STA pseudoaneurysm (asterisk) due to recanalisation of the external carotid artery with flow through the six mm vascular plug (white arrow; Amplatzer VP-II [St Jude Medical, Minnesota, MN, USA]). Under local anaesthesia and femoral access, the pseudoaneurysm inflow was occluded with a 7 mm polymer plug with anchor coil (IMP-07; Impede [Shape Memory Medical, Santa Clara, CA, USA]) deployed proximal to the previously placed device (B, red arrow). One year after the procedure, the patient was asymptomatic.Image 1

Production performance by polymer conformance control in ultra-low permeability heterogeneous sandstone reservoirs produced under their natural energy

For ultra-low permeability and highly heterogeneous sandstone reservoirs, fluid channeling along the high permeability layer leads to a rapid decrease of reservoir pressure coupled with very low sweep efficiency. As an effective conformance control technology, advanced polymer injection can enhance oil production from ultra-low permeability heterogeneous sandstone reservoirs, not only through conformance control but also through increasing reservoir energy. In order to simulate the reservoir energy storage capacity during the polymer injection stage as well as accurately control the energy release rate during the production stage, a novel experimental setup is assessed in this study. Partially hydrolyzed polyacrylamide (HPAM) is used as the polymer conformance control solution. Artificial heterogeneous sandstone cores are used to perform a series of polymer conformance control followed by production under the natural energy of the model reservoir. The effect of polymer injection volume and its concentration on polymer retention and plugging ability are investigated. Without polymer injection, the initial volume of produced liquid is large, however rapidly declines leading to a poor overall oil recovery. This trend accurately captures field performance. Upon advanced polymer injection, although the initial volume of produced liquid relatively decreased, the decline in the rate of liquid production decreases. The reservoir pressure in the later stages of production could still be maintained at a relatively higher level. Subsequently, the production period is prolonged, leading to a significant increase in oil recovery. The increase in the polymer injection volume or polymer concentration delayed polymer evolution from the reservoir, suggesting enhanced polymer plugging ability. Optimal polymer volume of 0.3–0.6 PV at its optimal concentration of 3000 mg/L corresponding to highest oil recovery is attained at the reservoir conditions. In this study, advanced polymer injection is proved to be a feasible technology to significantly improve the sweep efficiency in ultra-low permeability heterogeneous sandstone reservoirs. By controlling the appropriate polymer injection volume and its concentration, the highest recovery of a certain reservoir can be reached. For the oilfield engineers, by virtue of its ability to faithfully capture field trends, the proposed experimental setup may offer a reliable method to determine the optimal polymer injection volume and concentration for given reservoir conditions and characteristics.

Study on leakage plugging agent for steam well casing of heavy oil injection

This paper analyses the causes of the casing leaks of heavy oil thermal recovery wells, and analyses the trapping and sealing methods used in the current oil fields and their existing problems. Aiming at the problems of poor temperature resistance, insufficient strength, short plugging period and high cost for traditional cement and polymer plugging agents, a high temperature resistant plugging agent suitable for plugging in steam injection wells has been developed. The performance of the plugging agent was analysed and evaluated. The research shows that the high temperature-blocking agent has high strength, high temperature resistance, and high salinity and easily injected. It can withstand temperatures up to 300 °C and strength above 90 MPa. The plugging agent can meet the application requirements of the steam injection well.