Study On Dynamic Analysis Method Of Horizontal Well Production In High Sulfur Gas Reservoir

High sulfur gas reservoirs are characterized as deep burial depth and strong heterogeneity, and the hydrogen sulfide gas is highly toxic and corrosive. In order to achieve high yield with less well, more and more horizontal wells are used in the development of gas Wells. Accompanied with complex phase behavior change of high sour gas well, wellbore flow changed from single-phase gas flow into a complex gas-liquid sulfur or gas-solid sulfur flow in gas recovery process. And if the gas well production is less than the sulfur carrying flow rate, sulfur deposition will happen and an effect on production performance will exist. Therefore, in view of horizontal well production dynamic analysis in high sulfur gas reservoir, flow dynamic and the critical sulfur carrying model in horizontal wells should be analyzed based on the phase characteristics of high sulfur gas reservoir. At present few domestic scholars conduct a study in the field, so the results of research on the development of high sulfur gas reservoir is of important value as a reference.Through studying the rule of seepage flow and wellbore flow of horizontal wells, basing on the change of fluid phase state, the single phase and gas-liquid two-phase capacity coupling model of horizontal well is deduced in this article. The temperature-pressure model of simultaneous single-phase gas and gas-liquid or gas-solid two-phase considering the sulfur precipitation, combining with the prediction model of critical sulfur carrying in horizontal wells and considering the model of erosion flow, the comprehensive model of production performance analysis of horizontal well in high sulfur gas reservoir is established. The main completed work is as follows:(1) Based on the research of the PVT properties, dissolution and precipitation mechanism on elemental sulfur, we analyzed and comprised the feasibility of phase equilibrium prediction method and empirical formula method to calculate sulfur solubility, prioritized Chrastil empirical correlation to study sulfur solubility in this paper, and based on the measured solubility data in YB1H gas well, fitted out a new Chrastil experience correlation.(2) Considering the pressure drop of horizontal section in horizontal gas well, single-phase gas productivity coupling model is established. Computer software is used to programming and to solve the model. Based on the single-phase coupling model, considering liquid sulfur precipitation from the formation, the coupling model of gas-liquid two-phase horizontal well productivity is established.(3) Based on the C-S model, temperature and pressure prediction model of single-phase gas, gas-liquid sulfur two-phase, gas-solid sulfur two phase considering solid sulfur precipitation are established. Fluid and solid carrying for all section of horizontal wells are studied, resulting that the critical flow rate of horizontal section is greater than that of the inclined section and vertical section, so this paper adopts the horizontal section model to analyze and calculate liquid carrying.(4) Studying the quantity of sulfur deposition in wellbore and taking optimum diameter optimized into consideration, flow erosion model is deduced, combined with the dynamic model of inflow and outflow and the model of sulfur carrying in the horizontal wells, and a comprehensive model of production dynamic analysis of horizontal wells in high sulfur gas reservoir is established, also the model is compiled by Visual Basic6.0computer language.(5) Aimed at the actual production conditions of the typical high sour gas well YB1H in the gas reservoir of sichuan province and based on the comprehensive model developed, we conducted a study on the dynamic state of inflow and outflow and the capacity of moving with sulfur in horizontal wells, and the related sensitive factors are analyzed. Reasonable diameter optimized was76mm, the analysis found that sulfur precipitation existed in liquid form in the depth of3074, and sulfur transformed from liquid into a solid form in2821m. Besides the reasonable production proration range determined is62.5～73×104m3/d, and using fixed production working system is more reasonable in initial stage of exploration.