# Gassmann Inverse Dry Modulus & Fluid Substitution Wave State Calculator

> Gassmann Inverse Dry Modulus & Fluid Substitution Wave State Calculator is a paid API for AI agents from detect.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-11-04).

Performs complete Gassmann fluid substitution on a rock-physics model, computing the full wave-state (velocities, moduli, densities) after replacing one pore fluid with another.

## Facts

- Endpoint: POST https://detect.halowerk.com/v1/F-TD2000-GEO-INDUSTRY-B006/gassmann-inverse-dry-modulus-fluid-substitution-wave-state?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-04
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gassmann-inverse-dry-modulus-fluid-substitution-wave-state-calculator-ce9f0877
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jE02Ogid4XkaTbfW3C5hV

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability gassmann-inverse-dry-modulus-fluid-substitution-wave-state-calculator-ce9f0877 -d '<json body>'
```

Example prompt: Run a full Gassmann fluid substitution for a sandstone with mineral bulk modulus 36 GPa, mineral density 2650 kg/m³, porosity 0.20, initial saturated bulk modulus 22 GPa, shear modulus 10 GPa, initial fluid bulk modulus 2.2 GPa (brine, density 1050 kg/m³), and replacement fluid bulk modulus 0.07 GPa (gas, density 150 kg/m³) — give me the complete wave state after the fluid swap.

## When to prefer this

Use this endpoint when you need to perform rigorous Gassmann-equation-based fluid substitution on an explicit rock-physics model with known mineral, frame, and fluid properties. It is the right choice for reservoir characterization, 4D seismic feasibility studies, AVO modeling, and CO2 sequestration impact prediction where you have laboratory or log-derived elastic moduli and need to predict seismic response under a different fluid scenario. Prefer this over empirical velocity-porosity transforms when you have full Biot-Gassmann inputs available.

## Known failure modes

- Input values outside allowed ranges (e.g. porosity > 0.6 or < 0.01) return validation errors
- Physically inconsistent inputs (e.g. saturated bulk modulus exceeding mineral bulk modulus) may cause computation failure or unphysical results
- Missing required fields return schema validation errors
- Negative or zero moduli values rejected by min constraints
- Fluid bulk modulus exceeding mineral bulk modulus may produce unphysical dry-frame moduli

## How this service works

Calculate the complete fluid-substitution state of an explicit rock-physics model.

## Output

Returns the complete post-substitution elastic and seismic wave state of the rock, including: inverse-derived dry-frame bulk modulus, new saturated bulk modulus after fluid replacement, bulk density, P-wave velocity, S-wave velocity, and derived acoustic impedance — all computed via the Gassmann equations for the specified mineral-frame and fluid properties.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "artifact": {
   "type": "object",
   "required": [
    "gassmann"
   ],
   "properties": {
    "gassmann": {
     "type": "object",
     "required": [
      "data",
      "claim"
     ],
     "properties": {
      "data": {
       "type": "object",
       "required": [
        "mineral_bulk_gpa",
        "mineral_density",
        "porosity",
        "initial_saturated_bulk_gpa",
        "shear_gpa",
        "initial_fluid_bulk_gpa",
        "initial_fluid_density",
        "replacement_fluid_bulk_gpa",
        "replacement_fluid_density"
       ],
       "properties": {
        "porosity": {
         "type": "number",
         "maximum": 0.6,
         "minimum": 0.01
        },
        "shear_gpa": {
         "type": "number",
         "maximum": 200,
         "minimum": 0.001
        },
        "mineral_density": {
         "type": "number",
         "maximum": 10000,
         "minimum": 100
        },
        "mineral_bulk_gpa": {
         "type": "number",
         "maximum": 200,
         "minimum": 1
        },
        "initial_fluid_density": {
         "type": "number",
         "maximum": 5000,
         "minimum": 1
        },
        "initial_fluid_bulk_gpa": {
         "type": "number",
         "maximum": 100,
         "minimum": 0.001
        },
        "replacement_fluid_density": {
         "type": "number",
         "maximum": 5000,
         "minimum": 1
        },
        "initial_saturated_bulk_gpa": {
         "type": "number",
         "maximum": 200,
         "minimum": 0.01
        },
        "replacement_fluid_bulk_gpa": {
         "type": "number",
         "maximum": 100,
         "minimum": 0.001
        }
       },
       "additionalProperties": false
      },
      "claim": {}
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gassmann-inverse-dry-modulus-fluid-substitution-wave-state-calculator-ce9f0877/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from detect.halowerk.com](https://www.zero.xyz/host/detect.halowerk.com/llms.txt)