Water Analysis-- Supporting Stable Production

S ummary

Some amount of water is often co-produced from petroleum wells. Although co-produced water does not usually have commercial value, a great dealof information regarding the petroleum reservoir, which is needed for exploration and production, can be derived from analytical data from thiswater.
In addition to waters co-produced from wells, spring waters collected during geological field surveys, geothermal waters, plant waste waters, andriver waters collected for environmental surveying are analyzed and studied for reservoir evaluation and troubleshooting during operation.

Preparation and Wet Analysis

Analyses by Instruments (IC, ICP, LC, IRMS)

Before wet or instrumental analyses are performed, somecontaminated samples are pretreated.
In the field where no electricity is available, or in cases of urgency,
qualitative and quantitative wet analyses are conducted based oncolor changes and amounts of reagents consumed.

Ion chromatography (IC), inductively
coupled plasma-atomic emission
spectrometry (ICP), liquid chromatography (LC), and isotope ratio mass spectrometry (IRMS) areused to analyze dissolved ions, trace elements, organic acids,and isotopic ratios, respectively.
These instrumental analyses have higher precision andefficiency than the wet analyses.

Types of Water Co-produced with Oil and Gas

Evaluation for Risk Management of Scaling< Gas Pool>

W ater Rate

Cl-1Gas
2Transitional

3W ater
1 Cond ensed W ater
2 Transitional W ater
3 Form ation W ater

Two types of water — condensed water and formation water — areproduced from wells. Formation water becomes dominant as productivity
decreases. The ionic and isotopic compositions of these waters differ;
therefore, these data can be used to estimate productivity changes.

Evaluating the Effects of Stimulation

1,000濃度（mg/L）
Concentration

ClNH4+10,000

Mg2+80Fe2+,3+F‐
AlNa+70
60
50

Si40

1030

I‐

2011000010

Water chemistry data obtained from wet analyses and instrumental
analyses are used for many purposes, as described below:

90

Ca2+100

Key Points

100

‐

2030
4050
60
70
フローバック水累計
Cumulative amountof flowback（kL）
water (kL)

地層水混入割合（％）
Ratio of formation
water

100,000

Produced waters and waste waters experience various changes
in temperature and pressure. Such changes cause theprecipitation of minerals (scale), and these minerals can clog
tubing in wells or pipes in facilities.
Water analysis provides a solution for scale problems throughestimating the amounts of mineral precipitates

80

Acidizing is a stimulation method for low-productivity wells. Various
reservoir properties, such as the recovery rate of injection fluids, thetypes and amounts of minerals dissolved during acidization, and theproduction rate of formation water, can be obtained. From these data,
the effects of stimulation and changes in reservoir conditions can beevaluated.

(1) To understand the status of a reservoir for field development
and production operation(2) To reduce and resolve problems during operation(3) To explore new energy sources such as geothermal energy(4) To assess the environmental impact of exploration
Water analysis can contribute to many industrial projects such as
petroleum exploration, geothermal exploration, and environmental
assessment.

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