Horizontal Well Engineering Service Case

1. Data Collection：

Liaised with the client to collect and archive raw data records provided by all parties. Examples include: offset well completion data, wireline logging data, wellhead coordinates, target point coordinates, engineering and geological designs, etc.

2. Work Program Formulation：

Optimized the well trajectory based on regional build-up tendencies and the build-up capability of available positive displacement motors (PDMs), prioritizing a trajectory conducive to target landing. A preliminary trajectory control plan was submitted to the client for review. The final well work program was established upon mutual agreement reached through communication.

3. Bottom Hole Assemblies (BHAs) and Operational Requirements for Each Hole Section

BHA#1：（Surface Section）

Φ311.2mm PDC bit+Φ203 mm bent housing motor (1.25°/308mm stabilizer)+crossover sub+orienting sub+1 x Φ172mm non-magnetic drill collar (MWD)+Φ172mm crossover sub+6 x Φ172mm drill collars+16 stands of Φ127mm heavy weight drill pipe (HWDP)+Φ127mm drill pipe.

Vertical Section (0-450 m), primarily utilized slide-drilling combination, directional correction was performed as needed, the BHA was designed primarily for maintaining inclination.

BHA#2：（Intermediate Section）

Φ222.25mm PDC bit+Φ172mm bent housing motor (1.5°/212)+210mm stabilizer+float valve+orienting sub+1 x Φ127mm non-magnetic heavy wall drill pipe (MWD+GR)+16 stands of Φ127mm HWDP+Φ127mm drill pipe.

Vertical+Build-up+Tangent Section, (450m-1639.44m), primarily utilized slide-drilling combination, directional correction was performed as needed, the BHA demonstrated good inclination holding performance.

BHA#3：（Intermediate Section Build-up）

Φ222.25mm PDC bit+Φ172mm bent housing motor (1.5°/212)+float valve+orienting sub+1 x Φ127mm non-magnetic heavy wall drill pipe (MWD+GR)+3 x Φ127mm HWDP+multiple Φ127mm drill pipes+15 stands of Φ127mm HWDP+Φ127mm drill pipe.

Build-up Section (1639.44m - Target A),  slide and rotary drilling, building up the hole angle to 90.63°, adjust azimuth, (HWDP positioned above the 30° inclination section.)

BHA#4：（Intermediate Section Lateral）

Φ215.9mm bit+near-bit gamma sub+Φ172mm bent housing motor (1.25°/212)+210mm spherical stabilizer+float valve+near-bit gamma receiver sub+1 x Φ127mm non-magnetic heavy wall drill pipe (MWD)+3 x 127mm HWDP+multiple Φ127mm drill pipes+15 stands of Φ127mm HWDP+multiple Φ127mm drill pipes.

Lateral Section (Target A-Target B), drilled 1003.83m footage, slide and rotary drilling, trajectory controlled based on geosteering. (HWDP positioned above the 30° inclination section.)

4. Trajectory Control Measures:

（1）Select appropriate downhole motors. Adjust drilling mode and parameters promptly based on real-time survey data to strive for precise wellbore trajectory control.

（2）Optimize PDM bend angles to meet varying build-up rate requirements: Utilize 1.5° bent motors in vertical and build-up sections, comparing real-time inclination/azimuth with plan data. Use 1.25° bent motors in the lateral section, adjusting the length of oriented (sliding) drilling promptly to control inclination and dogleg severity (DLS).

（3）In the lateral section, control inclination during slide-drilling by managing parameters like weight on bit (WOB), rotary speed, and flow rate. Minimize the length and frequency of oriented (sliding) drilling to control trajectory and increase rate of penetration (ROP).

5. Additional Requirements

（1）Select PDMs with high torque output. Utilize bits with long gauge protection to enhance inclination holding and hole gauge stability.

（2）Strictly control wellbore quality per engineering design. Prevent deviation and drill straight in vertical sections. Survey interval ≤ 30 m. Increase survey frequency in collision avoidance intervals. Survey per single stand (≤ 10 m) in build-up and lateral sections. Ream promptly after taking surveys to prevent hole washout ('big belly') caused by localized circulation.

（3）Ensure sufficient inventory of HWDP, stabilizers, float valves (back pressure valves), and other tools.

（4） Rig solids control equipment must be complete and functional.

（5）All drill strings and tools run in hole must undergo non-destructive testing (NDT).

6. Key Issue Analysis and Mitigation Measures

（1）Mud performance directly impacts downhole safety and drilling efficiency. The long shale section in the upper part of this well necessitates optimized mud properties, especially controlling fluid loss to minimize false filter cake, reduce shale swelling/balling, and enhance lubricity. This effectively mitigates drag during directional drilling and improves ROP;

（2）Above 60° inclination (interbedded sand/shale): Enhance inhibition and control fluid loss. Increase lubricity beyond 60° inclination to reduce drag;

（3）Gas-bearing sand zones: Enhance drilling fluid bridging/sealing capabilities to control fluid loss；

（4）Maintain drilling fluid density at the upper limit of the design range to ensure well control safety and promote hole cleaning and stability;

（5） In the lateral section, desand and degas promptly. Avoid significant density fluctuations. In high-gas zones, employ controlled drilling time, keep the degasser operational continuously, and monitor inlet/outlet mud density changes;

（6）If drilling stops due to equipment repair or other reasons, prohibit extended circulation at the same depth to prevent hole washout and compromised build-up rates. The tool face must be oriented near 0° and the drill string must be reciprocated. Prohibit prolonged rotary motion to prevent sidetracking or unintentional inclination drop.

（7）Tripping operations require smooth handling. Avoid abrupt hoisting or lowering. Control running speed. Fill the hole every 20 stands while running in hole (RIH) and test tools. Do not force down if encountering resistance. Avoid reaming while RIH, instead, reciprocate and change direction.

（8）In the later stages of the build-up section or in the lateral section, if encountering drag or high friction, perform short trips promptly to condition the hole wall. Consider reversing the drill string configuration to ensure HWDP is positioned in the vertical section or above the 30° inclination depth.

（9）Strictly follow the directional engineer's instructions. Do not alter the BHA arbitrarily. The downhole blowout prevention tool (Float Valve) must be installed and functional to prevent annular sand from settling back into the drill string bore during non-drilling periods (e.g., repairs), which could cause tool sanding and necessitate unnecessary trips.

7.Operations Summary

The design was strictly adhered to during operations. The entire wellbore met quality standards. Total drilled depth accumulated 3,097m. Total lateral section length: 837.00m. Effective lateral length: 787.00m. Sandstone encounter rate: 97.59%.