Analysis on the influential factors about the cementing strength of shallow cementing in deep water

It is difficult to cementing shallow formations because of the low degree of consolidation and strength of the soil in the deep-water surface undissolved formations. In order to carry out shallow solidification reasonably, the factors influencing cementing strength ware analyzed in well design and construction. Based on the characteristics of surface soil in deep sea area of South China Sea, shallow cementing simulation was carried out by using similarity principle.The effects of cement strength, setting time and casing size on cementing cementability ware analyzed. The experimental results showed that the first and second cementing surfaces of high strength cement had high cementing strength.However, the strength difference between medium strength cement and low strength cement was not more than 20%, and the cementation strength of high strength cement tended to phase with that of medium and low strength cement as time goes on.Similarly, the cementing strength of the three kinds of cement sheaths increased with the increase of the waiting time, but the increasing trend of the interfacial cementing strength decreased gradually when the waiting time reached 18 h.The cementing strength of cement sheath varied with different sizes of simulated casing such as Ø50.8 mm, Ø76.2 mm and Ø114.3 mm. The research showed that the medium and low strength cement and high strength cement.The difference of cementing strength between high-strength cement and low-strength cement was relatively small, so it could be considered to develop medium-strength cement instead of high-strength cement for shallow cementing operation; the waiting time of shallow cementing could be reached.After a certain time node, the increasing trend of cementing strength slowed down, and the optimum waiting time window for shallow cementing could be studied later.The experiment using similarity principle to simulate field operation conditions was reliable.