高含量CO_3^-/HCO_3^-对泥浆的危害及其处理

HARM OF HIGH CONCENTRATION CO_3~=/HCO_3^- IONS TO DRILLING MUDS AND THEIR CONTROL

CO_3~=/HCO_3^-污染泥浆将引起泥浆粘切高、失水量大、难于处理、开泵时易蹩漏地层等一系列问题。本文分析了 CO_3~=、HCO_3^-的来源及危害,介绍了一些处理方法。

The pollution of drilling muds by high concentration CO_3~=/HCO_3^- has been ob- served in more than ten wells being drilled in Zhongyuan Oil Fields.Such pollution leads to significanlty increased viscosities and yield shear stresses as well as to very high (for low solid-phase polymer mud) or uneasily maintainable (for triple sulfopolymers mud) filtration losses.Polluted by CO_3~=/HCO_3^- muds are generally difficult to treat and consumption of chemical additives for their treating is abnor- mally high.In all the cases of pollution observed,CO_3~=/HCO_3^- ions are originated from Na_2CO_3 unnecessarily introduced into muds together with calcium acrylate pol- ymer additives or with bentonite.Polluted muds can recover their normal perform ante afler long standing over several days without any treatment or can be treated by using lime or lime plus gypsum in sufficient quantities all at once.Of common chemicals only FCLS gives notably thinning effect.The cases of treating polluted muds by using lime in two wells are described.