Bull Heading Method without Heavy Well Intervention for Annulus Cementing to Create Well Barrier prior to Shallow Zone Perforation in Mahakam Fields

Abstract

In order to maintain level of production on mature field of Mahakam, some shallow reservoirs are targeted to be produced from existing old wells. However, since the old wells were originally designed to produce reservoirs from deeper zone, there was not enough well barrier to perforate the targeted reservoirs on shallow depth. Annulus cementing is needed to create well barrier prior to shallow zone perforation. One of the challenge is marginal stakes of the reservoir which limit amount of budget that can be spend for the well intervention. Therefore, annulus cementing by bull heading method without heavy well intervention was selected. Bull heading annulus cementing method was performed to place cement column at designated depth by pumping cement from annulus-A and circulate liquid through tubing with some specific detailed procedure, i.e.: pump with high rate to minimize free fall of cement to create good cement quality, avoid cement entering the tubing by detailed cement placement and apply back pressure on the tubing to avoid u-tube effect. Avoiding cement to enter tubing is required to ensure no additional well intervention work needed to clear access in the tubing after cementing. The method has been successfully implemented on 3 wells so far. From operational point of view, this method is considered safer compare to other cementing method (no heavy lifting equipment needed), faster, more cost efficient and also proven to be able to create good cement quality as well barrier in the annulus.