Drilling

Oil and Gas Drilling

Drilling is the primary work procedure of extracting petroleum from subsurface reservoir within rock. Drilling operation perform by using specialized equipment known as drilling rig with supporting equipment of different services and specialized drilling team to reach at ultimate goal of hydrocarbon production successfully and safely.    

Drilling is most critical, risky & hazardous, expensive, target oriented & innovative work. Before drilling, it may need to ensure prospective geo structure by a process of seismic survey or related survey and by study of regional geology.   

Normally oil and gas drilling operation perform in onshore & offshore upon the location of prospective geological structure. In view of drilling work different types of rig are used like land rig for onshore, Jack up rig for shallow sea, Tender & Semi submersible rig for deep sea, means offshore.   

For the completion of drilling process might go through the procedures of planning, preparation of drilling site with rig & service equipment installation, specialized personnel in location and comply with health, safety and environment.  

For successful completion of drilling activities the following services are involved, mainly

            a) Drilling Rig is the main Contractor.

            b) Mud Engineering service

            c) Mudlogging service

            d) Cementing service

            e) Casing, Liner & Tubing service

            f) M/LWD and DD service

            g) Wireline and Slickline service

            h) Testing and Completion service

            i) Drill bit and Tools service

            j) Catering service

            k) Fishing service

            l) Transportation and Logistic support service

Overall Drilling field Supervisory, Administration and Wellsite geology provided by the International Oil Company (IOC).

Oil and gas sector comprise three main streams such as Upstream is exploration & production; Midstream is transportation, processing & refining; and Downstream is distribution & sale to end users.

A Leak-off test (LOT) - is one of the most common procedure to test the fracture pressure of the exposed formations. After cementing and drilling out of the casing shoe, the LOT is run to verify that the casing, cement, and formation can withstand the pressure needed to safely drill the next section of the well. Drilling engineers also rely on the reading from the LOT and use it as the maximum pressure that may be imposed on the formation to avoid fracturing.

Conditions for required accurate Leak-off test are :

• Drilling out the casing shoe and and approximately (5-25 ft) into new formation. 
• Circulating hole to condition mud to get uniform column of mud.
• Accurate pressure gauges.
• Accurate TVD and Casing shoe.
• Mud volume pumped untill leak-off starts.

Leak Off Test