Abstract

The development of light oil reservoirs in Kuwait is becoming increasingly important for maintaining the quality of exported crude. Moreover, it has been a crucial link to maintaining/increasing the oil production from this area. Thus, efficient testing of the light-oil reservoirs is of paramount importance for proper development.

Typical Kuwait reservoirs are low permeability, high pressure/high temperature (HP/HT) and sour. In earlier wells, the strategy had been to perforate these formations in mud with through-tubing guns. Results from testing in several wells indicated that if they could be perforated underbalanced, the formations would yield better results since this method would allow better penetration and perforation cleanup. A number of reservoirs are stacked horizontally and range from typically conventional to typically fractured limestone.

In view of the corrosive nature of the fluids, one of the primary efforts in the testing of these wells is directed toward keeping the number of wireline and coiled-tubing operations to a minimum without compromising the testing objectives. In view of need to individually test multiple objectives in the exploratory wells, special effort was directed toward finding methods that would effect a reduction in the testing period for each object. Thus, the overall savings would be significant.

There were several areas that required special consideration. This paper will discuss these areas, which are listed below, and how the challenges they presented were addressed:

1. Modification of retrievable completion test (RCT) tools used along with tubing-conveyed perforating (TCP) to test these zones in an efficient manner.

2. The challenges associated with designing and carrying out the tests.

3. Ongoing modifications in the testing methodology that were made to overcome the testing challenges.

4.The operation of annulus pressure-responsive components of the test string in the heavy oil based mud and difficult wellbore conditions.

5. How the problems of shaped-charge performance in the naturally fractured formations with unusually high compressive strength and very low matrix permeability and porosity were resolved.

6. The modifications to tools and methods that allowed the goals of the operator and service provider to be met are discussed.