Abstract:The South China Sea has been confirmed to be rich in oil and gas resources as well as natural gas hydrate resources. However， hydrate-bearing formations are often encountered during the drilling of oil and gas wells. Cementing is a critical step in oil and gas development. In deepwater drilling， the heat released during cement hydration can potentially induce hydrate decomposition， compromising formation stability and even affecting cementing quality. This study utilized numerical simulation methods， focusing on the hydrate-bearing formation at the SH7 site in the Shenhu area of the South China Sea GMGS-1 project. A numerical model for cementing was established to analyze the issues caused by cement slurry invasion into hydrate-bearing formations and the impact of cementing process parameters. The study found that an increase in cement hydration heat release rate significantly advanced the onset of gas and water influx， as well as increased its volume. The cementing pressure differential had a minor impact on the influx phenomenon， but it suppressed the influx when exceeding a certain threshold. Prolonging the pressure maintenance period significantly delayed the initiation of influx and reduced its volume. Therefore， it is recommended in practical engineering to use low-heat cement， extend the pressure maintenance period， and avoid excessively high cementing pressure differentials in the early stages to minimize hydrate decomposition and mitigate the occurrence of influx. This research provides a theoretical foundation for the cementing of hydrate-bearing formations， which is of great significance for enhancing the safety and efficiency of cementing operations.

Abstract:There are many researches on cementing implementation methods and engineering detection methods of cementing quality， but the analysis of picture results on cementing quality is relatively rare. In this paper， a text coordinate position reference algorithm for focusing image analysis range and an image analysis algorithm based on histogram similarity and gradient distance are proposed to evaluate cement quality using evaluation image. A combination of image analysis algorithm and business mechanism is used to extract quantitative data from the evaluation image to evaluate cementing quality. Through comparison of model experiments， the proposed image analysis algorithm can accurately identify the cement quality information in the picture， and the error rate between the analytic results and the actual results is less than 10%. The method proposed in this paper can effectively solve the shortcomings of low efficiency and large error of manual analysis， and provides a practical solution to the situation that electronic data of cementing quality is missing and only the cementing quality evaluation image is kept. The proposed algorithm has strong exploratory significance for deep mining of cementing quality pictures.

Abstract:Aiming at the problems of long horizontal section， complex wellbore conditions， difficulty in casing centralization， low displacement efficiency， and high performance requirements of cement system which restrict the improvement of cementing quality in shale oil horizontal wells， research on the collaborative optimization technology of drilling parameters and drill string assembly was carried out to meet the requirements of improving cementing quality for wellbore cleaning. In addition， the ideal casing centralization is designed by the simulation of displacement efficiency， and the integral stamping screw semi-rigid centralizer and the water displacement prestressed cementing technology are also optimized. Furthermore， the strength of cement paste is improved based on the toughness modification technology. The hydraulic fracturing requirements of shale oil wells can be met through ruducing the Youngs modulus and using the improved cement paste. All these work ensured the cementing quality of Well GY5-1-4H， so as to provide a worth considering key technology for long horizontal well cementing.

Abstract:At present, plastic casing and MTC material are used for cementing in sandstone uranium mining. This paper discusses the particularity of plastic casing cementing. It is not effective to detect the quality of plastic casing cementing with the instruments that test the quality of steel casing cementing. Thus, a JMTC—1 logging tool using the principle of measuring ultrasonic damping parameters was developed. The instrument can be applied to the cementing quality detection for casings of various materials. This paper introduces the design principle of JMTC—1 logging tool and its application in plastic casing cementing quality detection.

Abstract:Adjustment wells are mainly used for improvement of the well pattern through regrouping, and for fine production through subdivision of the payzone at the late development stage of the old oil fields so as to achieve stable or higher productivity. With the existing injectionproduction system and production status, the cement quality of the adjustment wells cannot ensure effective sealing between layers due to the complex formation pressure system and diverse formation fluid compositions. Based on the analysis of various technical difficulties faced by adjustment well cementation and their effects on cementing quality, this paper summarizes the existing problems with the cementing quality and the main technical measures to improve it at present, and put forward the technical measures and research directions to be taken in the next step, which lay a technical foundation for improving the cementing quality of adjustment wells.

Abstract:In order to improve horizontal well cementing quality in Honghe oilfield and meet the requirements of later staged fracturing, the horizontal well cementing technology in Honghe oilfield is studied. In view of the difficulties in horizontal section cementing, GSJ cement slurry system is selected through laboratory and field tests. Based on the measured formation pressure and formation rupture pressure, the balanced pressure cementing design is used to determine the annulus structure of slurry. In order to improve the displacement efficiency, the stabilizer type and placement location are optimized. The professional software simulation indicates that the centralized degree is more than 73%. High-quality well bore preparation and casing floating measure ensure smooth casing strings running down; the use of lengthened rubber plug, resin wheel rigid cyclone centralizer, shut-in valve and other accessories ensure the cementing quality. In the actual application in 53 horizontal wells, cement slurry all returned to the ground. CBL logging show that superior rate of cementing reaches 81.13%. This cementing technology is successfully applied in the horizontal wells in Honghe oilfield, which guarantees the cementing quality and meets the needs of later staged fracturing.

Abstract:Based on the shape and direction of different fuzzy membership functions distributional curve, we selected the fuzzy distribution which is suitable to describe the cement slurry’s thickening time, liquidity index, API fluid loss, compressive strength. By comparing the actual performance of cement slurry designed and measured with actual cementing quality score, we got the parameters of related membership function . Taking the 5 wells as an example, the results obtained from this evaluation method are verified by existing literature and the average fitting error of the cementing quality of the site is raised to -3.34% by -12.26%, which means this method can be used as a practical and reliable method for optimization of cement slurry system and admixture.

Abstract:In Tarim basin, Paleogene and Cretaceous strata contain cream and salt with active gas show, cementing is difficult. Based on the summarization on cementing failure causes of anti-channeling slurry with slight expansion latex in early stage, the characteristics of stratum lithology are mainly considered. With the purpose of improving the quality of second interface cementation, the anti-channeling saltwater mud system is selected out. This mud system has the characteristics of small API fluid loss, small SPN value and high cement paste strength. The field application shows the good quality of cementation in cementing process.

Abstract:The high-pressure formation has attracted high attention in the entire drilling engineering process of high-pressure oil and gas well, and there may be low-pressure thief zones in some of the high-pressure oil and gas wells. In the solidification period of cementing, cement slurry will have weight loss and fluid column pressure in the entire wellbore will be lowered. If the liquid column pressure is lower than the formation pressure in weightlessness well section, the formation fluid will invade the annulus to cause channeling, even lead to well control incidents; if the liquid column pressure is higher than strata (fracture) pressure, the formation leakage will occur, and further cause oil and gas reservoir pollution with less volume cement slurry returning. Therefore, proper handling the relationship between dynamic pressure and formation pressure and the formulation of relevant emergency measures are the key of success in high-pressure oil and gas well cementing.