Panel a shows a graph of flow rate inflow and outflow with injection pressure and backpressure over time, with stepped changes and averaged outflow values. Panel b shows a graph of injection pump volume decreasing while backpressure pump volume increases over time, with linear trends and equations indicating opposite trends. Panel c shows a graph with injection decreasing and backpressure increasing, with fitted linear relationships and R squared values. Panel d shows a graph of flow rate inflow and outflow with injection pressure and backpressure remaining relatively stable during a constant phase, and changing at start and end. Panel e shows a graph of injection pump volume decreasing and backpressure pump volume increasing over time, with linear fits indicating opposite trends. Panel f shows a graph with decreasing injection and increasing backpressure pump volume, with linear relationships and corresponding R squared values.Hydraulic test data for tests performed on natural clay samples prior to gas testing. (a) Inflow, outflow, injection pressure, and backpressure data for test BC2. The outflow data appears noisy because the data has been oversampled (logged every 30 s). (b, c) The change in volume of the injection and backpressure pumps. The gradient from this data is used to calculate flux and subsequently permeability. (d) Similar data to that of (a) but for test BC3A. Here, the injection flow rate exhibits a protracted transient, the cause of which is unclear but may be linked to the reduction in permeability of the sample observed during the test. The remaining images (e) and (f) are for test BC5 which show the change in volume of the injection and backpressure pumps during hydraulic testing