Reservoir Protection with Double Hydrophobic Agent in Jilantai Oilfield

The Hetao area is a fast deposited super-compensated basin, reservoirs in this area buried in less than 2000 m have notable characteristics of "three lows and one high", that is, low maturity, low permeability, low strength, and high shale content. The reservoir rocks have strong water sensitivity, extremely strong sat sensitivity, poor cementation, non-uniform particle sizes and high shale content. Poor cementation of the rocks makes it difficult to prepare core samples which are easy to break when wash with oils. Poor rock cementation also seriously affects the production rate of crude oil. A double hydrophobic agent and a filming agent were developed to deal with the strong sensitivity and poor cementation problems. Laboratory experimental results showed that a drilling fluid treated with the double hydrophobic agent and the filming agent can be converted into a double hydrophobic drilling fluid without affecting the rheological properties of the original drilling fluid. This drilling fluid is then able to turn the rock surfaces from being hydrophilic to hydrophobic, and coats the borehole wall with a film. In this way the reservoir is protected from the invasion of solids and filtrate and borehole wall is stabilized by the hydrophobic property and plugging behavior of the drilling fluid. The drilling fluid has been used on well Jihua2-209x and well Jihua2-322x, and it was found that with the double hydrophobic reservoir protection technology, the drilling fluid had stable rheology, low filtration rate and strong inhibitive capacity. Borehole wall was stabilized and a gauge hole was drilled. No downhole problems were ever met. Compared with other wells drilled nearby, the two wells were drilled with higher ROP and lower cost. The development and application of the double hydrophobic technology have provided a strong technical guarantee for the safe and efficient development of the Hetao area.