Deep tube well drilling is the process of boring a vertical borehole down to a water-bearing aquifer, installing casing and a screen to keep the hole open and filter out sediment, then fitting a submersible pump to extract groundwater for irrigation, industrial, or domestic supply. The right drilling method depends entirely on the soil and rock conditions at a given site - soft alluvial formations, hard rock, and everything between call for different rotary or percussion techniques, which is why the drilling method should be selected only after the subsurface profile is actually known, not assumed.
This guide covers the main tube well drilling methods used in Pakistan, what happens at each stage of the process, and how site conditions determine which method a project should use.
What Every Project Should Know Before Drilling
- Common drilling methods: Direct rotary, reverse circulation rotary, DTH (down-the-hole) hammer, and percussion (cable tool)
- Site investigation first: Electrical Resistivity Survey (ERS) identifies groundwater depth and aquifer potential before drilling begins
- Reverse circulation advantage: Effective for large-diameter wells and minimizes formation damage from drilling fluid
- DTH hammer use case: Fast, economical drilling through medium to hard rock formations
- Final stage: Well development (cleaning) is required after drilling to achieve full yield before pump installation
What Happens Before Drilling Begins?
Deep tube well projects should start with a subsurface investigation rather than drilling speculatively, since groundwater depth, aquifer thickness, and rock conditions vary significantly even across a single property. An Electrical Resistivity Survey (ERS) maps subsurface layers by measuring how different soil and rock formations resist electrical current, identifying the likely depth and extent of a water-bearing aquifer before any drilling equipment is mobilized. Skipping this step and drilling on assumption risks either missing the aquifer entirely or drilling deeper than necessary - both of which add cost without improving the outcome.
What Are the Main Tube Well Drilling Methods?
Different drilling methods suit different subsurface conditions, and the choice isn't a matter of preference - it's determined by what the ERS survey and local geological knowledge indicate about the ground being drilled through.
Direct Rotary Drilling
Direct rotary drilling uses a heavy-walled drill pipe rotated mechanically, with drilling fluid - typically bentonite mixed with water - circulated down through the pipe and back up around the outside, lubricating and cooling the bit while carrying cuttings to the surface and plastering the borehole wall to prevent caving. This method is well suited to drilling small to medium-diameter deep wells in soft to medium alluvial formations, the type of ground found across much of Pakistan's plains and river valley areas.
Reverse Circulation Drilling
Reverse circulation drilling uses the same basic rotary principle but reverses the fluid flow - water or drilling fluid is pumped up through the drill pipe rather than down through it, drawing cuttings up through the center of the pipe instead of the annular space around it. This method requires a larger rig and footprint but is particularly effective for drilling large-diameter wells, and reduces formation damage from drilling fluid contact compared to direct circulation, since the reverse flow path limits how much fluid pressure is forced into the surrounding formation.
DTH (Down-the-Hole) Hammer Drilling
DTH hammer drilling combines percussion and rotary action using a pneumatic hammer positioned at the bottom of the drill string, crushing rock into small chips that are flushed to the surface by compressed air moving up through the space between the borehole wall and drill pipe. This method is used for fast, economical drilling of boreholes up to roughly 200mm in diameter through medium to hard rock formations, making it the preferred choice wherever drilling encounters rock rather than soft alluvial soil.
Percussion (Cable Tool) Drilling
Percussion drilling, the oldest and most traditional tube well construction method, works by repeatedly raising and dropping a drill bit or auger string - either manually or by powered equipment - to break rock into small pieces that are then removed with a sand pump or bailer after being wetted. While largely superseded by rotary and hammer methods on modern projects for speed and cost reasons, percussion drilling remains a standard method in specific hard rock conditions where its mechanical simplicity is an advantage.
What Does the Full Drilling Process Involve?
Beyond the drilling method itself, a complete deep tube well project follows a consistent sequence of stages from site investigation through to a functioning, pump-ready well.
- Site investigation - ERS survey to identify aquifer depth and extent before drilling location is finalized
- Rig mobilization and setup - Positioning the drilling rig precisely over the surveyed location
- Drilling - Boring the borehole to target depth using the method suited to the site's soil and rock conditions
- Casing installation - Installing casing pipe to prevent the well from collapsing and to protect the extracted water from surface contamination
- Screen installation - Fitting a screen section at the aquifer depth, allowing water to enter the well while filtering out sand and sediment
- Gravel packing (where required) - Placing graded gravel around the screen in unconsolidated formations to further stabilize the surrounding soil and improve water entry
- Well development - Cleaning the well through surging, backwashing, or compressed air agitation to remove drilling fluid residue and fine particles, which is what allows the well to reach its full potential yield
- Pump installation and testing - Fitting and testing the submersible pump and motor to confirm output matches the well's actual capacity
Why Does Well Development Matter So Much?
Well development - the process of cleaning a newly drilled well through surging, backwashing, or compressed air agitation - directly affects how much water a tube well can actually produce, regardless of how good the drilling and casing work was. A well that skips proper development retains drilling fluid residue and fine sediment around the screen, which restricts water flow into the well and results in lower yield than the aquifer is actually capable of supplying. This step is often underestimated on cost-driven projects, but its impact on final well performance is significant enough that it shouldn't be treated as optional.
How Deep Can a Tube Well Go, and What Determines That?
Tube well depth is determined by where the target aquifer sits beneath the surface, which varies considerably by region and can only be confirmed through subsurface investigation rather than assumed from nearby well depths. Some areas have productive aquifers at relatively shallow depths, while others require boreholes extending several hundred feet or more to reach adequate water-bearing formations, with drilling method, casing requirements, and overall cost scaling accordingly as target depth increases.
How Do You Choose the Right Drilling Method for Your Site?
The right method depends entirely on what the ERS survey and drilling experience in the area indicate about subsurface conditions, not on a generic recommendation applied regardless of site.
How Karachi Tubewell & Pumps Approaches Deep Well Projects
Karachi Tubewell & Pumps has completed over 1,200 deep tube well bore projects across Pakistan since 2010, starting every project with an Electrical Resistivity Survey to map subsurface conditions and confirm aquifer location before drilling begins. Drilling method is matched to the specific soil and rock conditions found at each site rather than applied as a default, and every completed well is paired with correctly specified submersible pumps and motors sized to the well's actual tested yield. For projects requiring foundation-related drilling alongside water access, our soil investigation and pile foundation bore services extend the same subsurface expertise to structural applications.
Frequently Asked Questions
Duration depends on target depth, drilling method, and subsurface conditions, but most standard projects - from site investigation through drilling, development, and pump installation - are completed within days to a few weeks depending on well depth and site accessibility.
An Electrical Resistivity Survey identifies the depth and extent of the local water-bearing aquifer before drilling starts, giving a data-based target depth rather than relying on assumptions from nearby wells, which can vary significantly even over short distances.
Both are rotary methods, but direct circulation pumps drilling fluid down through the pipe and back up around the outside, while reverse circulation reverses that flow - pumping fluid up through the center of the pipe, which handles larger-diameter wells more effectively and reduces formation damage.
Low yield after drilling often points to insufficient well development, meaning drilling fluid residue and fine sediment haven't been properly cleaned from around the screen, restricting the aquifer's actual water flow into the well.
In many cases yes, depending on the well's original construction and current condition, though this requires an on-site assessment to confirm whether deepening the existing borehole is viable or whether a new well is the better option.