海上气田水平井井筒携砂机理研究

SAND-CARRYING MECHANISM RESEARCH OF OFFSHORE GAS HORIZONTAL WELL

南海西部海域S1气田稳定生产十余年后,由于地层压力衰竭、井下筛管腐蚀、生产制度波动等因素导致多口井普遍存在出砂现象,由于出砂造成油嘴及管线冲蚀严重,给地面安全生产带来重大隐患,只能通过调节油嘴大小以减轻出砂,这就导致气田产量大幅下降,很大程度上限制了气田的高效开发;出砂也会造成产层段砂埋,导致气井产能下降,为了进一步明确井筒出砂情况,开展井筒携砂机理研究。S1气田属于疏松砂岩储层,气藏由于埋藏较浅、岩石胶结性差,并且粘土和杂基质含量高,使得这类气藏在开采过程中容易出砂。地面能否监测到出砂,主要取决于井筒流体的携砂能力。文章中基于理论与实验研究了砂粒在水平井段以及垂直井段的沉降流动规律,该研究最终可确定砂粒在井筒中处于沉降、悬浮或上升的临界条件,对于S1气田在不产水或低产水条件下,临界携砂条件为产气量5~8×10~4m^3/d,此临界条件可为气井是否出砂提供判断依据,对于保障地面安全生产有重要意义。

After more than ten years ' stable production of the west of the south sea S1 gas field,due to formation pressure decline,downhole screen corrosion,and production system fluctuating,the wells sanding was caused.The choke and pipeline were eroded seriously,which brought the potential risk to the safety of the ground,only by adjusting the size of choke to alleviate the sanding,and this led to gas production declining obviously,which limited the gas field developing greatly.Sanding also can cause the reservoir to be buried too,which led to the decline of the gas well production capacity.In order to verify wellbore situation furtherly,the sand-carrying mechanism of wellbore was studied.S1 gas field is loose sandstone reservoir,the unconsolidated rock is easy to be sanding during exploitation.If the sanding is monitored on the ground,mainly depends on the sand-carrying capacity of wellbore fluid.In this paper,based on the theory and experiments,the sand flow regulation of settlement in horizontal well and vertical well section is studied,and the study finally can determine the sand in the wellbore as sedimentation,suspended,or upward critical condition.To the east 1-1 gas field under the condition of no water or low water,the critical condition of sand carrying is gas production for 5-8 ten thousand square per day,and the critical condition provides a basis for judgment in gas well sanding,which has an important meaning to protecting the production on the ground.