梁家楼油田硫酸钡锶垢成因分析

An Analysis for Occurence of Mixed Barium/Strontium Sulfate Scaling at Liangjialou Oil Field

梁家楼油田集输站及其外输管线结垢严重。垢样含无机物约95%,用X射线衍射法测定,该垢成分为硫酸钡锶Ba0.75Sr0.25SO4。根据4个集输站21口油井产出水水质分析数据,产出水富含Ba2++Sr2+和(或)SO42-,一般而言,生产层为S层的油井产出水富含Ba2++Sr2+,生产层为H层的油井产出水富含SO42-,两种水混合引起集输站及外输管线结垢。在4个注水站的回注污水中,Ba2++Sr2+和SO42-浓度很低或较低,远低于产出水中的相应浓度。2口井S层岩心薄片分析鉴定结果表明地层胶结物中含重晶石(BaSO4),且推论含天青石(SrSO4),这是S层地层水中成垢离子的来源,使一部分油井井筒或井口至集输站管线结垢,并造成该生产层不同油井产出水中成垢离子浓度的巨大差异。讨论了硫酸钡、硫酸锶的溶解度及温度、压力、含盐量的影响。将分别含4 mmol/L Ba2+、4mmol/L Sr2+8、mmol/L SO42-的3种溶液混合,生成的沉淀物经X射线衍射法检测,为Ba0.75Sr0.25SO4结晶,利用溶度积数据对该垢的生成作了初步讨论。

Serious scaling problems are encountered at oil-gathering stations and in their pipelines in Liangjialou oil field, Shengli. The scale substances comprise about 95% inorganics and the later is crystalline mixed barium/strontium sulfate, Ba0.75Sr0.25SO4, as determined by X-ray diffraction analysis. The water quality data of produced waters （PWs） in 4 crude oil gathering stations （COGSs） from 21 production wells show that these PWs are rich in Ba^2＋ ＋ Sr^2＋ and/or SO4^2-and, in general, the PWs from S pay layers contain high concentrated Ba^2＋ ＋ Sr^2＋ and the PWs from H pay layers SO4^2-; Mixing these two PWs at COGSs leads to scale formation in gathering installations and pipelines. In recycled PWs in 4 injection stations, the concentrations of Ba^2＋ ＋ Sr^2＋ and - are very low or much lower than that in the PWs from production wells. The core slice analysis for S pay layers of 2 wells demonstates barite （BaSO4） existed as a cementitious mineral and ratiocinates the existance of selestite （SrSO4）, from these minerals the scaling ions in PWs of S pay layers come from and result in scale formation in wellholes and in well to COGS pipelines of some production wells and hence giant differences in concentrations of scaling ions appear in PWs from wells of S pay layers. The solubility of barium and strontium sulfates and the effects of temperature, pressure, and salinity are discussed. The precipitate from the mixture of 4 mmol/L Ba^2＋ , 4 mmol/L Sr^2＋ , and 8 mmol/L SCO4^2- solutions is identified by X-ray diffraction as crystalline Bao.75Sr0.25SO4 ; the scale formation is discussed preliminarily on the basis of solubility product data.