Abstract
As a viscous offshore oilfield (600~2300 mPa·s at reservoir conditions), LD oilfield was developed by natural drive in early time. One well of the field initially produced around 20 m3/d with early water breakthrough until today. However, the production rate decline rapidly when the water production rate increased.
In order to improve the development effect, the cyclic steam pilot was founded. 12 horizontal wells were designed, two of which had been implemented. Through the comprehensive study, the injection parameters were optimized as follows: bottom hole temperature > 340°C, steam quality >0.4, injection rate equals 300 m3/d. The predicted oil recovery increases from 5% for cold production to 18% for cyclic steam injection.
In this paper we present the application and evaluation of the cyclic steam injection, which is a high quality steam injection with the miniaturization steam generator. For the evaluation of this thermal process for the first test well, an available history matched full field thermal model of the LD reservoir (Local refinement in space around the wells) was established.
Meanwhile, heat loss study of wellbore, decline rate analysis as well as suggestions about next well of this pilot project will be presented. The production effect of cyclic steam injection was compared with that of the cold production: peak oil production rate is 5.3 times and cycle oil productivity is 2.1 times of that for cold production; monthly decline rate is 23%;the valid time of first cycle is 200 days or more. The success of this pilot will provide technology and confidence for the better development of heavy oil in offshore oilfield of china.
