WPCI Treatments in a Deep HP/HT Production Hole Increase LOT Pressures to Drill Ahead to TD in a Gulf of Mexico Shelf Well
- David Allen Traugott (CSI Technologies) | Ronald Earl Sweatman (Halliburton Energy Services Group) | Randal Anthony Vincent (Chevron Corp.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 9-12 October, Dallas, Texas
- Publication Date
- Document Type
- Conference Paper
- 2005. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 1.12.1 Measurement While Drilling, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.10 Drilling Equipment, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 1.6 Drilling Operations, 2.2.2 Perforating, 1.7 Pressure Management, 1.12.6 Drilling Data Management and Standards, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 2.4.3 Sand/Solids Control, 1.11 Drilling Fluids and Materials, 5.1.2 Faults and Fracture Characterisation, 1.8 Formation Damage, 1.6.1 Drilling Operation Management, 3 Production and Well Operations, 1.2.3 Rock properties, 1.2.2 Geomechanics, 2 Well Completion, 1.14 Casing and Cementing, 1.12.2 Logging While Drilling
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This paper covers two wellbore pressure-containment integrity (WPCI) treatments that substantially increased the pressure- containment integrity in 852 ft of open hole in the last sidetrack for the production hole section. This ultimately saved having to set pipe early, which could have jeopardized the commercial discovery of a lower gas sand. Earlier side tracks attempted unsuccessfully to bypass the loss/flow problems that would not allow drilling ahead and increasing the 18.0-lb/gal mud weight (MW) to drill into a high-pressure zone on adeep, high-pressure/high-temperature (HPHT) well in the western Gulf of Mexico shelf offshore Louisiana. Various lost-circulation material (LCM) treatments were used with no success increasing the hole's pressure containment.
The WPCI treatments raised the leakoff test (LOT) across the entire 852 ft of open hole up to 19.1 lb/gal equivalent (ppge) vs. the lower LOT of 18.3 ppge before the first WPCI job. LOTs were performed before and after each of the two WPCI treatments to measure improvement in the hole's pressure-containment integrity. This LOT data helped prove that apparent fracture gradients can be simultaneously increased in multiple numbers of layers and different types of weak formations exposed in long, open holes by inducing near-wellbore, flexible stress cages created from WPCI treatments.1-4 This can then allow use of increased MWs and drilling pressures to prevent excessive gas influx from high-pressure sands without lost circulation (LC) in adjacent weak zones.
The paper discusses the WPCI treatment design and job procedures, including treatment optimization by the analysis of data from openhole wireline/logging while drilling (OHWL/LWD) logs, cuttings lithology, fracture-seal location indicators (torque on bit [TOB]/weight on bit [WOB]), and before/after LOT pressures. Real-time operations5 also described allowed remote expert analysis and support for wellsite personnel to (1) interpret formation characteristics for optimized treatment design and (2) analyze treatment pressure/rate data for selected placement of WPCI sealants.
The western shelf region in the Gulf of Mexico is known industry-wide as one of the most challenging areas to drill for oil and gas. Faulted formations, HPHT conditions, abnormal pressure ramps, depleted reservoirs, and LC are only a few of the major challenges operators must meet on a regular basis. To deal with these issues, precise knowledge of well conditions and carefully planned contingencies are required.
The structural map in Fig. 1 shows in detail the many faults associated with this area. The well path associated with the example wellbore encountered many of these faulted areas and these fault lines show why pressure-integrity issues were encountered while drilling this well (Fig. 2). The main reason this well encountered so many pressure integrity problems was that the mud-weight window (MWW) was too narrow.
Two weak zones were clearly identified before the WPCI job: one just below the shoe at 17,628-17,710 ft measured depth (MD) or 16,038 ft total vertical depth (TVD) and the other at 18,480-18,520 ft MD (16,679 ft TVD). Before the WPCI treatments, the maximum MW of 18.0 lb/gal was too low to hold back the lower production sand. As soon as the MW was increased, the well started losing fluid to these weak zones up the hole.
A number of conventional LCM treatments were used to try and stop mud losses; the treatments produced limited success and were unable to increase the WPCI of the well.3,6,7 Finally, on the second sidetrack, two WPCI treatments were used to increase the pressure-containment integrity from 18.26 to 19.1 lb/gal. These treatments allowed an increase in the MW to 18.3 lb/gal with no losses and permitted drilling ahead through the production sand to total depth (TD). A summary of the well problems encountered before the WPCI treatments is presented in Table 1.
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