低渗透含硫化氢气藏储层改造中的难点及对策

PROBLEMS AND COUNTERMEASURES TO STIMULATE SOUR GAS RESERVOIRS WITH LOW PERMEABILITY

我国含硫化氢气藏大部分成熟度较高,天然气中硫化氢含量的高低明显地受储层的岩性控制,天然气中硫化氢主要来自干酪根中含硫有机物的热解和储集层中沉积硫酸盐(石膏和硬石膏)的细菌还原作用或高温热化学还原作用,其储集层具有埋深大、地温高、物性条件差的特征。含硫气藏储层特性和硫化氢强烈的还原性给储层改造提出了诸多挑战。水力压裂对低渗透含硫气藏改造的适应性很差,酸压是目前我国含硫气葳储层改造最有效的增产措施,但仍面临严重的单质流沉积和硫化亚铁沉淀对储层的二次伤害问题。要提高对含硫气藏储层改造的成功率和改造效果,有效地解决储层改造中的控硫控铁难点问题,必须立足于对含硫化氢气藏储层特性和硫化氢特定理化性质的系统研究,弄清高温、高压、高含硫条件下Fe(Ⅱ)-H2S、Fe(Ⅲ)-H2S的反应特性、储层酸- 岩反应机理及酸蚀裂缝导流能力的影响因素,提出针对性强的酸液体系与酸压工艺。

Most of sour gas reservoirs have high level of mature in China. The H2S content of gas is governed by the reservoir lithology obviously. The H2S comes mainly from the pyrolysis of sulfurous organisms in the kerogen and the bacterial reduction or the thermo-chemical reduction of sulfate (gypsum and anhydrite) depositing in the reservoir. The reservoirs characterize big buried depth, high formation temperature and poor physical property. Great challenges appear for the reservoir stimulation because of the features of the sour gas reservoirs and the strong reduction of H2S. Hydraulic fracturing is not suitable for the stimulation of sour gas reservoirs with low permeability. Acid fracturing is the most effective measure for the stimulation of sour gas reservoirs in China now. But it has to face the serious problems of secondary reservoir damage since the deposition of mono-sulfur and the precipitation of iron protosulfide. To improve the success rate and the results for the stimulation of sour gas reservoirs and effectively solve the problems of controlling iron and sulfur in the reservoir stimulation, the systematical study must be conducted for the features of sour gas reservoirs and the special physic-chemical property of H2S to understand the reaction characteristics of Fe (II) -H2S and Fe(III) - H2S, the reaction mechanism of acid-rock and the effect factors of conductivity of acid-etching fractures under the conditions of high temperature, high pressure and high sulfur content. Based on the study, the corresponding acid-fluid system and acid-fracturing technology are proposed.