Preliminary Study on Air Injection in Annuli to Manage Pressure during Cementing

AbstractAlong with the development of low permeability reservoirs, underbalanced drilling technology is applied more and more widely. During the cementing operation of underbalanced drilling wells, cementing liquid can flow into the reservoir more easily for the absence of the mud cake, which certainly weakens the reservoir protection advantage of underbalanced drilling. Based on the methods of underbalanced drilling and managed pressure drilling, a new method of cement technology, Balanced Pressure Cementing Technology by Air Injection in Annuli, was put forward. The calculation models of the maximum depth of injection point and the maximum start-up pressure were built. Considering the power limitation of the pump, valves of gas lift were introduced and the calculation method of valve location was developed. This technology could effectively control the annulus pressure of wellbore, assure the cementing quality and protect the hydrocarbon reservoir, thus reduces the exploration and development cost

Effects of chitosan treatment on strength and thickening properties of oil well cement

The research objectives were to investigate the influence of chitosan on strength and thickening properties of oil well cement under the downhole temperature condition. The results showed that the chitosan has the ability to increase the thickening time, but due to chelating Ca2+ ion, it may cause consistency wave at initial stage, and shorten thickening time at higher dosage and higher temperature. Chelating pretreatment will weaken the retarding effect of chitosan. Effects of LMW chitosan on strength and thickening properties are more acute than that of HMW chitosan. Because of increasing induction period, the pre-chelating LMW chitosan extends thickening time

Novel Low Complexity BP Decoding Algorithms for Polar Codes: Simplifying on Non-Linear Operations

The parallel nature of the belief propagation (BP) decoding algorithm for polar codes opens up a real possibility of high throughput and low decoding latency during hardware implementation. To address the problem that the BP decoding algorithm introduces high-complexity non-linear operations in the iterative messages update process, this paper proposes to simplify these operations and develops two novel low complexity BP decoding algorithms, namely, exponential BP (Exp-BP) decoding algorithm and quantization function BP (QF-BP) decoding algorithm. The proposed algorithms simplify the compound hyperbolic tangent function by using probability distribution fitting techniques. Specifically, the Exp-BP algorithm simplifies two types of non-linear operations into single non-linear operation using the piece-wise exponential model function, which can approximate the hyperbolic tangent function in the updating formula. The QF-BP algorithm eliminates non-linear operations using the non-uniform quantization in the updating formula, which is effective in reducing computational complexity. According to the simulation results, the proposed algorithms can reduce the computational complexity up to 50% in each iteration with a loss of less than 0.1 dB compared with the BP decoding algorithm, which can facilitate the hardware implementation

Novel Low Complexity BP Decoding Algorithms for Polar Codes: Simplifying on Non-Linear Operations

The parallel nature of the belief propagation (BP) decoding algorithm for polar codes opens up a real possibility of high throughput and low decoding latency during hardware implementation. To address the problem that the BP decoding algorithm introduces high-complexity non-linear operations in the iterative messages update process, this paper proposes to simplify these operations and develops two novel low complexity BP decoding algorithms, namely, exponential BP (Exp-BP) decoding algorithm and quantization function BP (QF-BP) decoding algorithm. The proposed algorithms simplify the compound hyperbolic tangent function by using probability distribution fitting techniques. Specifically, the Exp-BP algorithm simplifies two types of non-linear operations into single non-linear operation using the piece-wise exponential model function, which can approximate the hyperbolic tangent function in the updating formula. The QF-BP algorithm eliminates non-linear operations using the non-uniform quantization in the updating formula, which is effective in reducing computational complexity. According to the simulation results, the proposed algorithms can reduce the computational complexity up to 50% in each iteration with a loss of less than 0.1 dB compared with the BP decoding algorithm, which can facilitate the hardware implementation

Research and Application of Slag Activity Stimulation at Low Temperature

AbstractAiming at the problem that slag has low hydration rate at low temperature, physical and chemical stimulation to slag are studied. The results show that, physical stimulation increases the slag reaction contact area, and effectively improves the slag hydration reaction rate. Chemical activator JFJ-1 can significantly promote the activity of slag and enhance the slag's compressive strength. The optimum adding amount of JFJ-1 is 5%. Under the condition of 10°C, the compressive strength of low density slag cement slurry develops much more fast for the use of JFJ-1 and the strength can reach 6.8MPa in 24h, 16.4MPa in 48h. Laboratory tests show that the low density slurries has no free fluid and good rheology

Data from: Effect of carboxylic group on the compatibility with retarder and the retarding side effect of the fluid loss control additive used in oil well cement

The retarding side effect and the compatibility with other additives are the main problem to limit the field application of the fluid loss control additive (FLCA) synthesized. The effect of the type and content of carboxylic acid group on the retarding side effect of FLCA and the compatibility between FLCA and the retarder AMPS-IA synthesized by 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and itaconic acid (IA) was studied in this paper. The type and content of carboxylic acid group have a great influence on the fluid loss control ability, the compatibility with retarder and the retarding side effect of FLCA. FLCA containing IA or maleic acid (MA) shows better compatibility with retarder than FLCA containing acrylic acid (AA), but the retarding side effect of FLCA containing MA is weaker than that of FLCA containing IA, so MA is the most suitable monomer to synthesizing FLCA having good compatibility with retarder AMPS-IA

The application of coated superabsorbent polymer in well cement for plugging the microcrack

The research objectives are designed to realize the application of superabsorbent polymer (SAP) in well cement to plug microcrack. Gypsum-chitosan-gypsum coated SAP is proposed. Percolation theory is used to research plugging microcrack mechanism. According to the exact analytical solution of square plane percolation threshold, dosage threshold of coated SAP microspheres is calculated as 28.40%, which can deliver the plugging of microcrack. The method of manufacturing quantitative microcrack is established, and self-designed instrument is employed to test plugging performance. The results show the ability of plugging microcrack when the dosage of coated SAP microsphere is higher than the threshold

Low elastic modulus and expansive well cement system: The application of gypsum microsphere

The research objectives in this paper are designed to use gypsummicrosphere to achieve low elastic modulus and expansive well cement system. Results show that gypsum microsphere has the ability to compensate for volume shrinkage of hardened cement. Expansive crystals produced by the reaction of tricalcium aluminate and dihydrate gypsum exist around gypsum microsphere. Though compressive strength of hardened cement is improved by gypsum powder, existence of massive crystals increases brittleness of cement sheath. Compared with gypsum powder, due to porous structure, gypsum microsphere decreases elastic modulus of hardened cement, which shows brilliant resistance to stress and strain

data about intrinsic viscosity, API fluid loss and setting time

data about intrinsic viscosity, API fluid loss and setting tim