The Analysis Of Borehole Stability And Sanding Production Forecast In Huangyanl-1,2-2Gas Field

The problem of borehole stability is always presence in petroleum engineering, which preclude the development of drilling engineering. Before the formation drilled, the rock underground maintain balance under the action of overburden pressure,the maximum horizontal stress and the minimum horizontal stress.The borehole rock had been removed, and the borehole wall rock has lost the support, replaced by the drilling fluid hydrostatic pressure after the borehole opened. The bore stress around redistribution, so that strong stress concentration in the vicinity of borehole. If the rock strength is not large enough,the borehole instability phenomenon occurs. The borehole instability is always creating a series of accidents, such as borehole collapse,loss circulation,blow-out and jamming etc.Which will extend the construction cycle, even scrap the well. Therefore,it is very important to ensure borehole stability in order to achieve a safe, efficient, high quality and economy drilling.The object of paper is Xihu depression structure in the East China Sea Basin. The borehole collapse,loss circulation,blow-out and jamming always occur during the drilling.At the same time, the depth of the well is deep in this block and the operating cycle is long. Therefore,the risk of borehole instability is very big.The content of this paper includes:(1) The statistics and analysis of accidents, complication in Huangyan1-1,2-2gas field;(2) The rock of reservoir strength experiment in Huangyan1-1,2-2gas field;(3) The ground stress’s direction as well as magnitude in Huangyan1-1,2-2gas field;(4) The regularities of distribution of pore pressure, ground stress, caving pressure, fracture pressure in Huangyan1-1,2-2gas field;(5) The prediction of probability of sanding in Huangyan1-1,2-2gas field.The paper take advantage of loging dates, drilling dates to analysis the borehole stability of Huangyan1-1,2-2gas field. We make sure keep borehole stability on the basis of precise pore pressure. The pore pressure can be predicted taking advantage of logging dates. Making use of the drilling, logging and core data to study the borehole stability of the Huangyan1-1,2-2gas field. Pore pressure is foundation to study the borehole stability.We cann’t eatablish reasonable safety mud window if having not accurate pore pressure. Making use of acoustic logging data to establish the formation pore pressure model determine the vertical profile of pore pressure through the drilling, logging and core data from the study of rock mechanics.Using log determine the mechanical parameters of rock data through the empirical formula, which study stress measurement methods and forecast model of continuous stress and determine the formation of tectonic stress coefficient prediction model. Using layer stress model continuously calculate the stress, collapse pressure, fracture gradient and the leakage pressure, establish the corresponding pressure profiles. Through the analysis, it gains the reasonable safe mud weight window of Huangyan1-1,2-2gas field according to the difference of hole deviation angle and azimuth angle. It is very ioportant to accurately predict the sanding of oil and gas fields in the producting, which can guidance the choice of measures sand prevention. The paper researches and analyses many sanding prediction models, then predicts the sanding situation of the Huangyan1-1,2-2gas field.