Study of core strength characteristics as an indicator of the volume distribution of the Temposcreen-Plus polymer-gel system

Filtration experiments are widely used in the oil and gas industry. They are used to determine the key physical and chemical characteristics of the porous medium, the parameters of fluid filtration. Also, filtration experiments are the main method for evaluating the residual resistance factor for compositions that are used in water shut-off technologies. However, filtration studies are not sufficient to study the distribution of the filtrate over the volume of the porous medium. This paper describes a method for using strength characteristics studies to evaluate the distribution of the polymer-gel system "Temposcreen-Plus" in the pore volume of the core after filtration. A method for representing core strength data in the form of a visualized image of the hardness distribution on a color scale is also proposed. Keywords: strength characteristics; hardness; core; "Temposcreen-Plus"; filtration experiments; visualization.

A Successful Field Application of Polymer Gel for Water Shutoff in a Fractured Tight Sandstone Reservoir

The wide existence of fractures makes conformance control by polymer gels more challenging in water-flooded oil reservoirs. Selection of an applicable gel system and design of an intelligent approach for gel treatment are key components for a successful field application. Moreover, selecting the candidate wells and determining the injection volume of gel are also critical to the success of gel treatments. A gel system with adjustable polymer concentrations was applied for conformance control in fractured tight sandstone reservoir, and notably, less than 5% of syneresis was detected after aging for one year at reservoir condition. The viscosity and the gelation time of this gel system can be adjusted according to the targeted reservoir conditions. The pilot test was conducted in Huabei oilfield (China), and the oil recovery after water flooding was only about 20% original oil in place (OOIP). With further exploitation of the oil field, the majority of the reservoir has suffered from poor sweep efficiency and extremely high water cuts. To characterize the distribution of fractures, the seismic coherence cube was utilized. In addition, the pressure transient test, interwell tracer test and the injection-production data were used collaboratively to determine the volume of fractures in the reservoir. The option of gel formulation and the determination of operational parameters are mainly based on the wellhead pressure. According to the seismic coherence cube, the zone of candidate well group shows a weak coherence state, indicating that numerous fractures exist. Furthermore, there is good continuity between the candidate injection well and the production well. According to the pressure transient test, the volume of re-open fracture is about 1730.9 m3, while the volume of micro-fracture is about 4839.4 m3. Comparably, based on the interwell tracer test, the estimated volume of fractures is approximately 3219.7 m3. Consequently, the designed volume of gel for treatment is 1500.0 m3 in total. The properties of gel slugs were carefully designed, which was tailored to the specific wellbore conditions and formation characteristics. Three months after the gel treatment, the average oil production was increased from 0.36 t/d to 0.9 t/d, and the water cut was decreased from 95.77% to 88.7%. The improved oil production was still benefited from this gel treatment after one year. This study provides a comprehensive approach, from optimization of gel formulation, followed by selection of candidate wells, to calculation of the injected volume, to design the viable operational parameters, for gel treatment field application in fractured reservoirs. It shows that, besides a gel system with superior properties, a suitable injected volume of gel may enhance the chance of success for gel treatments.

Investigation of the mobility of dispersed gels of the Temposcreen polymer-gel system

The article describes the method of optical-electronic observation of the process of sedimentation of gel particles in the polymer-gel system. The analysis of hydrodynamic movement of gel particles in laminar and turbulent modes during the implementation of the Temposcreen technology in oil production is carried out. The effect of hydrodynamic conditions on the mobility of the polymer-gel system in well and reservoir conditions, as well as on the distribution of the dispersal gel phase in the reservoir, is considered. On the basis of the graph theory, the model of fluid flow management in the oil layer by the Temposcreen mobile polymer-gel system is presented.

A Novel Branched Polymer Gel System with Delayed Gelation Property for Conformance Control

Summary Excessive water production from oil reservoirs not only affects the economical production of oil, but it also results in serious environmental concerns. Polymer gels have been widely applied to decrease water production and thus improve oil production. However, traditional polymer gels such as partially hydrolyzed polyacrylamide (HPAM)/chromium (III) gel systems usually have a short gelation time and cannot meet the requirement of some conformance control projects. This paper introduces a novel polymer gel system of which crosslinking time can be significantly delayed. A branched polymer grafted from arginine by the surface initiation method is synthesized as the backbone, chromium acetate is used as the crosslinker, and no additional additives are used for the gel system. The results show that the gelation time of this system can be delayed to 61 days at 45°C and 20 days at 65°C because of the rigid structure of the branched polymer and the excellent chromium (III) chelating ability of arginine. The polymer gels have been stable for more than 150 days at 45 and 65°C. Coreflooding and rheology tests have demonstrated that this branched polymer has good injectivity and shear resistance in high-permeabilityrocks.

Successful Gas Shutoff Operation Using a Coiled Tubing Telemetry System: A Case History

Summary In a deviated well in the Caspian Sea, the gas/oil ratio (GOR) increased rapidly in 2017. The result was an oil rate decline with several choke backs to manage GOR buildup. After performing two production-logging jobs, it was confirmed that 76% of the gas production was coming from four upper perforations. The main objective was to perform a gas shutoff (GSO) treatment in two stages to reduce gas production by squeezing polymer into the formation and setting packers at a 59° deviation inside a 9⅝-in. casing for temporary isolation of the middle and lower production sands. Fifteen runs were performed with a tube wire-enabled coiled tubing (CT) telemetry (CTT) system that consists of a customized bottomhole assembly (BHA) that instantaneously transmits differential pressure (DP), temperature, and depth data to the surface through a nonintrusive tube wire installed inside the CT. For the first time in the region, a tension, compression, and torque (TCT) subassembly was deployed to control the entire setting/retrieval process with accurate downhole upward/downward forces. CTT technology was a key element to successfully set two through-tubing inflatable retrievable packers (TTIRPs) by performing casing collar locator correlations at the tubing end, which was 133 and 228 m [measured depth (MD)] shallower from the setting depths. In addition, during the second GSO operation, the GSO gel system crosslink time was modified on the basis of the actual bottomhole temperature (BHT) recorded with the CTT system. Finally, during the third GSO operation, treatment placement was improved, spotting more GSO gel system inside the casing section and avoiding further treatments. After successful placement of the GSO gel system, a drop from 15.5 to 4.5 MMscf/D in gas production was observed (GOR reduction from 11,000 to 750 MMscf/bbl) with an oil rate increment from 1.4 to 6.04 Mbbl/D. Furthermore, after the gas reduction, the operator was able to produce between 1.5 and 2.0 Mbbl/D from other wells that were choked back on the basis of gas handling capabilities limitations. In the short term, GOR reduction sustained at 3,000 MMscf/bbl and 3.0 Mbb/D oil rate. The novelty of using the CTT system and TCT subassembly for real-time monitoring of BHA data proved to be beneficial for positioning two TTIRP, modifying GSO gel system design, placing it precisely across target intervals, and retrieving two TTIRPs that in the end provided direct and positive financial impact for the operator.

Formulation and Evaluation of A Nanoparticle Laden in Situ Gel System for Enhancing the Ocular Delivery of Ciprofloxacin

The human eye can be a tricky issue for topical administration of the drugs due to its unique anatomical arrangements of surface tissue and corneal impermeability. Topical instillation of drugs in the form of eye drops is the major and well-accepted route of administration for the treatment of varied eye disorders. Conventional ophthalmic drug delivery systems often lead to poor bioavailability and thus reduced therapeutic response. Several new preparations are developed to enhance the contact time of the medicament on the surface of the eye. Successful results have been obtained in the form of inserts and collagen shields. However, these preparations have also some disadvantages, such as poor patient compliance, particularly in the case of elderly patients. These problems could be solved by using nanoparticles laden in situ gel-forming systems that exhibit phase transition from solution to gel. These nanoparticle in situ gel systems may be formulated as eye drops suitable for administration through instillation into the eye, which upon exposure to the eye, stimulated by various ocular physiological factors, converts to the gel phase. The advantage of those formulations is that unlike inserts and films they do not require complicated equipment for manufacture and that they are scalable without any difficulty. The objective of the present study was to prepare a pH-dependent nanoparticle-laden in situ gel system for Ciprofloxacin, to prolong the release of the drug into the ocular compartment. No incompatibility was found between the drug and the excipients. Nanoparticles were developed using the nanoprecipitation technique. Eudragit RL 100 was used as the polymer. While the in situ gel solution was formulated using chitosan as polymer. The Ciprofloxacin nanoparticles were measured for particle size and the average particle size was ranged from 295.3-458.7 nm. Entrapment efficiency ranged from 13.83% to 6.29%. Nanoparticleladen in situ gels had the pH of the formulati