First Application Of Thermal Activated Resin As Unconventional LCM In The Middle East
Authors: Knudsen Kristen , Leon Gustavo Adolfo , Sanabria Andres Eduardo , Ansari Adel , Pino Rafael Miguel 
Published: March 2015

One of the major challenges when drilling gas wells in offshore fields is to drill under high pressure and in a loss circulation zone in intermediate hole sections. Heavy mud is used to control the pore pressure in a narrow operational window that create losses and as a consequence, well control issues. Several solutions/ideas have been implemented while drilling this intermediate section, including a thermal-activated resin, rigid rapid fluid treatment, used to regain full circulation and successfully increase the window gradient.

The solution to these challenges was developed by designing a fast setting, thermal-activated resin LCM liquid plug with a density equal to 152 pcf. This new treatment slurry was able to be bullheaded and displaced with a polymer mud 152 pcf. The slurry was easily pumped through drill pipe, MWD and drill bits.

This paper presents case histories and field applications of this novel polymer-based lost circulation material, for successful treatment of heavy mud losses to formation in wells in offshore gas fields in the Middle East. The paper also includes a discussion of the methodology, material properties and applications.

INTRODUCTION

There have been many papers over the years referring to why loss of circulation occurs, the different materials available and how to solve it during drilling and while cementing. Basically, loss of circulation treatments can be divided into two categories:1) those where the loss circulation is solved by the addition of solid materials to the drilling mud; and2) those where the problem can only be solved by the use of a non-mud system.

Normally when loss of circulation occurs, the first attempt to cure the problem is always by a reduction in mud weight and/or the addition of granular, fibrous, or lamellated material to the mud, but in many cases without success. If no success is obtained by using the solids-laden mud, then it becomes necessary to use the most efficient non-mud system available.

Loss of circulation is one of the most time-consuming and costly problem faced by oil and gas well drilling industry. The loss of drilling mud results in increased drilling time, loss of expensive mud, plugging of productive formations, and / or loss of well control.

This paper presents a non-mud system solution prepared for challenging field cases in the Middle East where severe drilling fluid loss were encountered. In the cases, thermal activated resin was used to cure drilling fluid loss.

LOSS OF CIRCULATION

Loss of circulation is the partial or complete loss of drilling fluid or cement during drilling, circulation, running casing, or cementing operations. After the loss of circulation occurs, the level of the drilling fluid in the annulus may drop and then stabilizes at a particular level depending upon the formation pressure.

Loss of circulation problems may be encountered at any depth when the total pressure used against the formation exceeds the formation pressure. Commonly, four types of formation are responsible for loss of circulation (Figure 1):a-) natural or induced fractured formations;b-) vugular or cavernous formations;c-) highly permeable formations, andd-) unconsolidated formations.

Loss of drilling fluid can result in increased cost, loss of time, plugging of potentially productive zones, blowouts, excessive inflow of water, and excessive caving of the formation. Therefore, application of an immediate solution to loss of circulation is an essential part of drilling engineering.

LOST CIRCULATION MATERIAL

Fluid loss is encountered in almost all drilling operations. Depending on the severity of lost circulation and the size and type of the thief zone, different lost circulation materials (LCM) are used for curing.

LCM is an additive to drilling fluids, cement slurry or frac fluid penetrating a formation. LCM are either insoluble or water soluble and are typically granular (most common), flaky or fibrous. LCM pills are pumped down a well and spotted to build up an impermeable layer on the formation face causing the loss of circulation problem. Sometimes two or three pills are used to stop losses.

In most cases, viscous mud pills with loss circulation material allow to temporarily reducing the losses but do not guarantee a durable plugging of the formation. Also, cement plugs can be used but their placement and the time necessary to drill through them make their use relatively costly.